Uhh, there's no more Umbrella, it died, they stated that in RE4, so they couldn't come after Barry since they don't exist.

Steve is so totally dead, I played CVX, HE IS SO TOTALLY DEAD, Wesker stole his body for the T-Veronica Virus.

Jill's "last escape" thing was also a comment about her just getting out of the whole dealing with Umbrella and zombies stuff, which to be honest I'd be pretty sick of if I were her.

Leon IS too busy with his new job, and besides, he wouldn't be back in another game after he had RE4 all to himself as well as RE2, two games, they can't give him a third.

So what if HUNK is in documents? He appears in one in RE2, and the 4th Survivor mini-game, I don't remember any in RE3, but he had an epilogue. He's just a mini-game character, and besides, he works (or rather worked) for Umbrella, they're not around any more so realistically neither should he.