Ge'ula

Mashiah has not come by Pesah, as was predicted by some that he would.
Should we be discouraged?

No.

First of all, it's still Nissan, and there's still a chance that it will happen this month. In fact, Rav Biniyahu Shmueli, even after Pesah (according to gog1.com), said that the Final Redemption is at the doorway. Also, gog1.com said earlier that the midway point of the 7-year war will happen on Pesah Sheni of this year (May 23^rd, 2005). So there is still a lot to look forward to.

Why now more than any other time in history?

Well, no other time in history were there so many predictions from so many different rabbis. Also, these rabbis aren't just making up dates. There are solid Kabbalistic reasons for their predictions. Certain world events and other time-related reasons drove those predictions.

And, what will be if it still doesn't happen by the end of the year?

I will still have Emunah Shelaimah that it will happen eventually, as the greatest predictors, our Nevi'im, are always true to their word. Rabbi Akiva was absolutely convinced that Bar Kochba was the Mashiah. When it turned out not to be the case, he remained the greatest of his generation. There's never a reason to get discouraged.

Let's hope it happens soon!