First things first, if you don't want to spoil anything for yourself by reading a description of some footage from Joss Whedon's Avengers: Age of Ultron, then you might want to stop reading now. I just know that some people like to read this kind of stuff, and I happen to be one of them.
A sizzle reel from the film was recently screened in the UK where Marvel Studios president Kevin Feige was holding a preview and Q&A for Guardians of the Galaxy. Thanks to Radio Times, we have description of the footage, which Feige said will probably never be shown again. I hope they screen something at Comic-Con this year! They have to! Anyway, here's the description they provide, which includes the Hulkbuster!
"Known as the ‘Hulkbuster’ in the comics, it looks like Stark’s normal red and gold armour after hitting the gym, and is almost the size of the Hulk himself. Where his normal suit is sleek as a missile, this is bruising like a tank. It’s the iPad to the original’s iPhone, Frasier to the original’s Niles. There’s no word on why the two heroes are fighting, but the Hulk doesn’t need much reason to get in a scrap. You can see some concept art of the fight above: it actually looks better here than the very unfinished footage we saw.
"Also sighted were new brother sister duo Scarlet Witch and Quicksilver. Scarlet has mysterious reality warping powers (in the footage this mostly involved making some blocks float around) while Quicksilver can run really, really fast (although without the special effects, it was more of a light jog). Scarlet Witch was shown fighting alongside Hawkeye on a ruined Italian street, but earlier in the reel both she and her brother were locked in fancy Perspex prison cells. Designed by Stark out of the ruins of his New York penthouse, this has all mod cons: floor to ceiling windows, twin laboratories for Stark and Bruce Banner, and parking for supersonic jets. It’s reminiscent of the SHIELD helicarrier in terms of construction, with lots of shiny metal pillars."
Sounds awesome to me! Now we just need to see some footage from the film ourselves. Please let it be Comic-Con! Plllleeease!