Hmm, now this is odd.
The Bioshock games have been on Microsofts list of upcoming backwards compatible 360 games for a while now, with no promised release date or any news for a long time. If they're really releasing a remastered collection, that would explain why they've been stalling it so long, and it would probably mean they'll cancel the backwards compatible releases.
It's a shame with the potential BC cancellation, but at the same time, a native remaster would probably perform better with regards to resolution and frame rate.