Has Bioshock Infinite been delayed again, and for what reason?

Bioshock Infinite was initially going to release on October 16th, but was then pushed for the expected February 26th 2013 release, but has it now been delayed again???

It might have been pushed for a march 2013 release, which isn't too terrible since it's only an extra month wait, but why would they do this? Best guess, Unreal Engine 4. It was revealed at E3 that the first game to use Unreal Engine 4 would be released in 2013 but they didn't say which game it would be, at this point any game could be the one. Could Bioshock Infinite be the game to start using UE4, or could it be any other 2013 release like Tomb Raider, Aliens: Colonial Marines, or an unknown title? Also, what do people think about delays?

Check out screenshots for the new Unreal Engine 4

It seems like everything uses Unreal Engine 3 now, which of course is true. But the world is changing, things eventually get replaced and newer and potentially better replacements emerge. The next step, being Unreal Engine 4, is expected to fully unveil at E3 but we got screenshots to examine, check em out: