I'd love to see a solo Hawkeye film. He's got a number of solo books to pull from and the current comic focusing on what Hawkeye does when he's not an avenger is excellent source material. As a guy without crazy super powers, there's a lot more opportunity to character build versus the non-stop action we get from most of the Avengers. Truth be told though, I'd love to see Phase 4 be a "West Coast Avengers" storyline where Hawk creates a sister team out in California.
A West Coast Avengers spinoff might be the right vehicle for Hawkeye to grow as a character in the MCU. There are also his roots in SHIELD to consider, and he was mentioned in passing during last night's Agents of SHIELD
. But seeing the cosmic/global nature of the threats that the Avengers are facing, I don't know if the whole West Coast team concept makes as much sense in the context of the MCU as it did in the comics back in the 80's and 90's.
I thought I heard mention of Mockingbird, so maybe they're already going this route.
Mockingbird has actually been featured in the past couple of episodes of Agents of SHIELD
. So far she's been interesting, and I think they're working to develop her into more than just a featured character. I hope they do. Because Adrianne Palicki is HOT!!!!
In the comic, Stark handed the IM gig over to Rhodey, so Black-Iron-Man and later War Machine were a big part of that team. Would be a cool way to keep the Avengers going if RDJ and the other big names want a break or just limit their involvement to cameos akin to Sam Jackson's Fury.
This would be a cool way to utilize someone who's as strong of an actor as Don Cheadle. And expanding on his independent role as War Machine/Iron Patriot would be worth examining. To that end, I also have to wonder if he's also going to be a factor in the Captain America 3 story line.