To reiterate what some pple are saying here:
1) Yaakov Avinu lost his nevua so he shouldn’t be able to pass on when the “keitz” or the end of days will be
2) I think that we are supposed to learn from the miscalculation at cheit ha-egel, as well as the miscalculations of SEVENTY years (see posts above) which all the kings and even yidden miscalculated in the time of Achachveirosh and the purim story (ie when the geulah/2nd bais hamikdash would happen, why achashveirosh made a party in the first place, etc)
I think we are supposed to be learning from our history that the calculations are not exact ACCORDING TO OUR CHESHBONOS, though I am sure it will be clear to us once Mashiach does come…but the dreams etc clearly mean we are getting closer – but we can’t know if that means tomorrow or in 15 years…let’s just do our best to be chozer b’teshuva and be the best ovdei hashem that we can be, to be yidden who are growing in their yiddishkeit rather than the opposite, and be”H let’s hope we will be zocheh to see mashiach and the geula in our lifetime, amen!
(…as well as seeing the said gedolim – I heard in a shiur that anyone who is truly “tzipisa l’yeshua” – truly awaits the geula & mashiach – then besides for the official techiyas hameisim that will happen in olam haba years after mashiach, there will be a “mini techias hameisim” for every gadol, person, etc who truly awaited mashiach, to get to see mashiach when he comes! I don’t know the source, however – if anyone does please let us know! 🙂 )