I think it's worth noting that Boubouille from MMO-Champion does not think there will be an Alpha tomorrow. In fact, he doesn't think there will be an Alpha at all this time around.

http://www.mmo-champion.com/general-discussions/ff-alpha-tuesday/msg1985508/#msg1985508

I'm not saying Boubouille is necessarily right, but he has a pretty good track record, and if I had to make a bet, I'd typically place my money on MMOC over WoW.com. He doesn't provide any details on why he thinks this, so this could just be his own personal theory.

My own personal theories placed the alpha starting on February 2nd (the same day I speculate that the final wings of ICC will be unlocked, similar to how the WotLK alpha started the day Kil'jaeden was unlocked in the Sunwell). Predictions that alpha will start tomorrow are certainly within the realm of possibilities.

If it does start tomorrow, we'll probably know within the next 24 hours. If it doesn't, there will probably be debates whether or not it's started and just under tight wraps, and every week we'll have speculative posts on the forums and WoW.com about whether or not the alpha will go live that week.