Unfortunately, ASW is a small company, and that usually means they don't get the preferential treatment or attention that more well-known and larger companies get. It would be nice if ASW could give a red flag to Microsoft, but I don't think Microsoft would bat an eye if a niche franchise like BlazBlue became exclusive to PS3 or if ASW made any other similar such move.
While I don't actually have a lot of experience with Xbox Live yet, from what I've seen on Windows Live it's noticeable that Microsoft doesn't take their problems very seriously (As per the 2 month wait.) Unfortunately, they have a lot of money to spare so even if ASW or the Blazblue title were as big as say, Resident Evil and Capcom, I still have my doubts they would flinch.
Not to say I've given up on Valk myself, but just that the way I try to look at it is, the longer we wait - the less time we have to go. Obvious, but it does provide some sort of comfort. "Anything worth wanting is worth waiting for," or however that saying goes, eh?