Wasn't DMC 2 stated to be 6 months after DMC 1, or has that since been disavowed?
DMC2 takes place last chronologically, in the "far off future". Basically Capcom can squeeze as many games as they want to in before it. They kept it far off until they decide how to tie into it, or carry on from it. Pretty much as others have said: until they decide whether or not it should be canon anymore.
Just replayed/beat it recently (as in maybe 1 hour ago), I'd be alright if they took it out of canon or just kept it a "side story"