I'll go out and say it here that everybody and their mother following the art and beta progress was speculating who the elf was. Most people, from what I could tell at the time, was saying that the elf was Marithra. It was strengthened by the idea that, if Ysera were to come back, it would be through leapfrogging deus ex machina means, which people felt that Blizzard wouldn't be stupid enough to use. So, natural conclusion, it would be Marithra.
Well - one thing leads to another, and... it is what it is. Now that it's clear that it's Ysera, everybody who was wrong before is saying, "Oh, no, it was obvious that it was Ysera, I know Ysera like the back of my hand." God, please.