Oops missed Dante ... anyway, yeah it sounds like Collison is somebody they really like a lot ... I think it's a good move.
1) Rudy wants to be gone and doesn't really have a role here any more with the Matthews signing.
2) Bayless behind Miller might get 12 minutes a night and would have almost no minutes at the 2 with Matthews here, he won't stay content for long, and I'm dubious about his longterm prospects of ever becoming a capable point guard (minimum of 2 years if ever).
3) Dante is also going to be a low minute reserve, so the opportunity cost isn't as great as it appears (I do like Inferno quite a bit though, losing him would stink).
4) Joel may never be healthy enough to provide meaningful production.
Final roster if this move happened:
Miller/Collison/Johnson?
Roy/Matthews/Williams
Batum/(Matthews)/Posey/Babbitt
LMA/(Camby)/Pendergraph/(Babbitt)
Oden/Camby/(Pendergraph).
()=secondary position
I like that team's chances quite a bit.