After the end of next season (when ever that is), Nash will come off contract at the same time Carter comes off contract and Petreus comes off contract. In other words, we will be in a position to go seriously into the free agency market. Currently, HoopsHype has the Suns at $28.6 million,
http://hoopshype.com/salaries/phoenix.htm. If you adjust for two mid first round picks, and other adjustments, the Suns will still be able to sign at least one top player and have above the MLE available even if they cannot con somebody into taking back some spare people such as Wrrick and Lopez. I don't think they'll move Brooks (or make him available as RFA) unless they could get a shot a big time PG.
IMHO, nobody will trade for Nash except to get his expiring contract. Talent wise, he' not worth more than a late 1st rounder due to his age. Realisticly, the only teams that have interest as a player are deep in the playoffs and their picks suck.