This is silly. Right now it's far more likely that Melo forces a trade to Boston. Both scenarios are ridiculous, but if you were going to put money on one... put money on Melo to Boston. Melo can opt out of his contract at the end of THIS season, his team is 9-19 with no draft picks. There's a real fear out there that he'll sign with the Lakers this summer (they have cap space to make it happen and are currently in the midst of tanking for a lotto superstar)...
Boston, meanwhile, has plenty of assets to make it work. They could offer Green, Humph's expiring contract, one of the youngs and as many draft picks as possible.
While it's possible Rondo could hold his team hostage and demand to be traded, Rondo doesn't have a no-trade in his contract. Boston will have opportunities to trade Rondo over the next year ... even if the offers are "Asik + Lin" or "Granger + George Hill", those deals will be better than what the Knicks have to offer. By all means, Rondo could sign with NY in summer 2015, but if that looks like a possibility, Rondo will be gone by Feb 2015.