Presumably this is a move to open up more PT for Harrington as well. It's pretty obvious that management is looking for multi-position players, so I wouldn't write off Freddy just yet. He's one of the more versatile guys on the team and I'd expect that he'll get a reasonable offer.
If Jones' stock explodes like James Jones or Brad Miller, I say let him go -- obviously its not worth another huge contract just to have him come off the bench.
If we somehow get rid of Jackson, yeah I'd want him resigned. But not if someone drastically overpays him because he's a restricted free agent.
I agree with what you said about versatile players. Granger and Shawne Williams can both play the 4, 3 and probably 2. If we get Al Harrington he can play both the 4 and 3. Jackson can already play the 3 and 2.
I want another power forward though, maybe a second year or undrafted rookie we can sign at the minimum. Incase JO or Al gets injured. We only have 11 players under contract (12 if we sign Harrington).