I think you have to start with the premise you need all time elite talent to win a championship. There is some chance Rondo gets to that level - but I'm thinking he's only ever at the second fiddle level. Historically there are (SWAG alert) ~5 teams that won the championship in 50 years without having an all time talent.
2008 C's had KG (arguably the top PF of all time) who actually has more of a supporting game (great D, good blended offense, not dominant on offense) and they had the perfect compliment in Pierce (get the winning bucket wing) and the perfect SG to play next to Pierce. Rondo and Perk were solid role players (which is where Perk remains today) and Posey was a great 6th man who essentially backed up all of the starting 5 (due to the positional flexibility of the starting 5.)
So let's assume Rondo can be the second guy, we need an elite guy. The best guy that we could get is probably Durant, but I think it's a very long shot. He seems like a guy who will keep taking the max and staying as long as Presti is improving the team (and unlike CLE's management Presti is likely to make smart moves.) Of the guys we could conceivably get this summer, I could see Amare or Johnson as players we'd have a path to - but Johnson isn't that much of an upgrade over Ray. Amare - not sure he's good enough offensively to make up for his D to be your prime guy.
You start looking further out - let's say they get Ray Allen and Pierce into affordable deals over the next two summers 8-10 range, that starts to give them flexibility. So I think you have to look at some sort of trade in 2011 ofseason or FA move in 2012 to see a significant transition. I think Denver has petered out by then - Billups, Martin, Nene are all getting old in the tooth and Melo might look to move on. (As for concerns about Melo - everyone forgets that Pierce had similar concerns from the rest of the league a few years back and even a lot of posters on this site.)
Jefferson is just a pipe dream - I'd like to see him back in green, and I think Minny would move him - just not sure we can get him. Bogut was just a name I pulled out of my posterior.