2K Games' China studio is currently in the process of moving the original BioShock from last-gen consoles and PC to iOS. BioShock is a "premium" iOS game and thus carries a "premium" price, however, that price is unknown thus far, but we'd put it somewhere in €10-30 range. The game itself is 7 years old (I know, right?) so I can't imagine it being too expensive, but it will definitely be more expensive than your typical app.
The game itself will not look as stunning as it did on consoles and PC, as in-game lighting and shadows are cut down pretty dramatically, as are a lot of the art assets. If you're not obsessed with high quality gaming, this will be just fine.
The gameplay will still be the same, thankfully. Touch play is an option, but you will also be able to use a bluetooth controller that works with iOS. Meaning, you could potentially play BioShock on-the-go, which would be amazing.
BioShock iOS doesn't come with any of the extra downloadable content that the console/PC version has. It requires a newer iOS device -- iPad Air, iPad Mini 2, iPad 4, iPhone 5S, iPhone 5C or iPhone 5. It will not run on any older devices, unfortunately, but if you're an iOS user, I doubt you're surprised.
Bioshock will hit iOS during the summer, but does not have a set release date yet.