I haven't seen any confirmation of a 30 day date. Not sure where that is coming from Dead Money was exclusive for two months.
And either way, it is insulting to treat PC and PS3 consumers as second-class citizens.
Microsoft bought the rights awhile ago, it even says so on UESP (I know its the
Unofficial Elder Scrolls Pages but it's still reliable.). It's actually for both the first and second expansions. Also, if the expansion turns out to be a flop, you'll know and won't have wasted your money on it.