The following is what Rambam has to say in regards to speculating about the Messianic age, and speaking about when it will occur (emphasis added):
Regardless of the debate concerning these questions, neither the order of the occurrence of these events or their precise detail are among the fundamental principles of the faith. A person should not occupy himself with the Aggados and homiletics concerning these and similar matters, nor should he consider them as essentials, for study of them will neither bring fear or love of God.
Similarly, one should not try to determine the appointed time for Moshiach's coming. Our Sages declared: 'May the spirits of those who attempt to determine the time of Moshiach's coming expire!' Rather, one should await and believe in the general conception of the matter as explained.
(Rambam, Hilchos Melachim 12:2)
And yet, I still hear speeches and talks all the time that are basically built upon the premise that we are in the “age of redemption”, or some such claim. Or that any day now the Moshiach will arrive, and the exile will end. Or that it is certainly the end of time, and that “things are winding down”, and any moment now the world as we know it will cease to be.
I think such discussion and statements are misguided and not worthwhile — as did Rambam. I do recognize that, for some people, such statements can really motivate them to do better — but it’s all on a faulty premise. We don’t have any clue when Moshiach is coming, or what the preceding age will be like. We don’t know anything about the era of redemption, really. And any claims about its timing, of course, cannot be either verified nor disproven. They’re typical of a particular style of motivational speeches — in which things are stated that cannot be verified in any way — but, fundamentally, saying that we’re “towards the end, now” is meaningless. Is it another month? A year? A decade? A century? A thousand years? Given that the universe is billions of years old, “towards the end” could mean quite a while indeed. So why bother even talking about it when we don’t have any idea what we’re really talking about in the first place? (Which is precisely Rambam’s point.)
And how long will whatever positive effects such statements bring out in people really last? A couple days? A couple weeks? Some people will be told their whole lives that Moshiach will come “any day now”, and when it doesn’t happen quiet that soon, what happens to their faith in this tenant of Judaism? We're supposed to believe that it will, eventually, happen. That is a feasible thing to maintain belief in. Belief that it's coming at any second, only to be repeatedly let down? That seems difficult to maintain, and is not part of the halachic belief system anyway.
The Year 6,000
And then you have this whole “6,000 years” thing that gets thrown around all too often. The trouble is that it’s not really clear what any of the sources for it mean. The oldest source for such a concept is to be found in the Gemaras Sanhedrin and Avodah Zara:
Rav Kattina said: ‘The world will exist for 6000 years and one (thousand) of destruction’ ... We have a teaching which is in agreement with Rav Kattina, as the seventh is the sabbatical year – one in seven years. Likewise the world will rest 1,000 in 7000 … ‘a thousand years in Your eyes are like yesterday which has passed …’ [Psalms 90:4].
(Sanhedrin 97a)
The world will exist for six thousand years: two millennia of void (“tohu”); Two millennia of Torah; and then two millennia of the age of Moshiach.
(Avodah Zarah 9a)
Putting aside the fact that it’s unclear if aggados of this nature are meant to be taken literally, what does this even mean? What point in history, exactly, does the clock for 6,000 years start counting? Maybe it’s already passed? Maybe we’re already in the next period? And do these two Gemaras not contradict each other, on some level? Does the world end in the year 6,000 after some sort of destruction, or does the destruction begin then, followed by a renewal of the Earth? And so on and so forth.
Oh, and one should also note that neither of these sources mention the fact that the Moshiach will come after 6,000 years have elapsed. It would seem, actually, according to the second Gemara that we’re already living in the Messianic age. And the first source doesn't even mention Moshiach at all!
And while I recognize that there are other sources that say other similar, but notably contradictory, things about there being some significance to 6,000 years from “creation” (again, whatever that point in time means), come the year 6,000 and nothing happens, I can’t say that I’ll really be bothered all that much, and nor should we be. Point is, like Rambam said, none of this stuff is clear, and so we shouldn’t waste our time over-analyzing it, or talking abouy how soon it will happen. It won’t bring us any closer to God, in any real, substantial, lasting, or profound way.
Rav Kanievsky
I also thought that I would take a moment just to point out that we really should be careful when we hear stories about Rav Kanievsky, or similar great sages alive today, proclaiming that “Moshiach is at the door”, or some similar thing. Again, aside from the problems listed above in terms of how long “at the door” means, there is a more fundamental problem: The stories very often aren’t true.
I’m not saying that they are never true, or that great sages don’t hint, or explicitly say, these things from time to time (I mean, Ramban, for one, did, after all). But very, very often these stories are just not true or verified at all.
I cannot find the source for it at the moment, (UPDATE: Found. Here it is.) but I remember reading that someone once asked Rav Kanievsky why he didn’t speak out against the various misquotes in reference to him saying Moshiach’s arrival is imminent. He replied that those who are really seekers of truth would make it their business to verify what was actually said. Indeed, if he was to stay on top of everything wrongfully quoted in his name, it would be a full time job, no doubt.
(I’m reminded of the old adage that some Rabbis would tell their students: “You can quote my Torah in your name, but don’t ever quote your Torah in my name”.)
What Will It Be like?
Finally, it’s worth nothing what, approximately, things will be like during the Messianic era. Again, we certainly do not know anything for sure, but there’s a nice little article I found on the subject that quite nicely states the following:
From the Prophets, Talmud and Midrashim, we know what universal changes Moshiach will bring about. Among them: the whole world will return to God and His teachings; the entire Jewish People will be gathered back to the Land of Israel; the royal dynasty of King David will be restored; Jerusalem and the Third Temple will be rebuilt; the Temple service will be restored, along with the keeping of the Sabbatical Year (Shmitah) and the Jubilee Year (Yovel); the Sanhedrin, the religious supreme court of the Jewish people, will be reestablished.
(Sources for these things can be found in the comments section of the post.)
A dream worth waiting for, whenever it is that God will decide to make it a reality…