If its a multiplayer pack, I hope its MP only. Don't mix it with single player stuff.
i agree that'd be a better policy. i've never been big on MP TBS games; they take too long.
but even if the expansion is just new jewelry and MP, i'll still pay for it.
with the amount of feedback they've been gathering, i think we can fairly expect a more.
as tempted to speculate as i am, i think it'll be better to hold off until they release more details. besides, i've got the simpsons movie to be obsessed with for now (i saw it at midnight this morning... i want to see it again... NOW! stupid work)
edit:
I cant imagine another release by the end of the year.
i know, i think that's what most surprises me. on the other hand, they have been rather quiet lately... i'd written it off as focus on other game projects, but if they've got another expansion brewing up, that'd be so far beyond my expectations.