Looks like Ken has improved but at 40 he can't have too many good fights left in him. Even as good as he looks now training with Paulson, I'd hate to see him against Fedor, Mino or even Arlovski.
Yet I think Frank Mir is actually a decent matchup for Ken. Plus it would be a great fight to finish his UFC contract because a loss to Mir with a good showing would be admirable while a win would obviously end Ken's career on a magic note. I seriously think Ken has a reasonable shot here. Experience is huge in this sport, Ken may have better standup and he's had 12 years of submission practice with some of the best.
He's not the best in the world, but he matches up well with Mir - its all about matchups!