It would be a bold move, but I can totally see this happening. Bruce Banner and The Hulk were easily the best things about The Avengers, largely because of Mark Ruffalo's excellent performance - making him the best Banner of the lot, by far - and Whedon's hilarious interpretation of the character. The fact that rumours of a standalone Hulk movie have been quelled says a lot about Marvel's approach to the character - he needs to be shown off in fits and starts, so that audiences don't get tired of the big green guy. Thus, if The Avengers 2 is the crescendo of Phase Two of the MCU, I could easily see The Hulk dying either a) before the final battle, to make the situation seem even more desperate, or b) succumbing to his wounds after the final battle, setting a bleak tone for Phase Three. The Hulk's death needs to be an iconic, watershed moment, and so you can be sure that if Joss goes for it, he won't be taking it lightly; it will matter, and have a huge impact on the MCU. Chance Of It Happening: 6/10