if Novartis or Bristol were the partner then a combo might conceivably be of interest to them.
Why would Ariad management be so stupid as to have one of them as a partner when both of these corporations have spent hundreds of millions to develop their billion dollar blockbuster drug....? Novartis or Bristol could simply use Sprycel and Tasigna as front-line (raising billions in revenues) and use '534 only against mutations. Sure, there's money in the second and third line (a lot of money) but I think that unless Ariad is getting massive amounts of money upfront, it doesn't make sense for them to partner with a company that already has a first or second line TKI.
If I were Ariad, I would only be considering a drug company that doesn't have a drug for this indication yet, and a company that intends to go head to head and pound NVS or BMY. See: MRK, LLY, CELG, SNY....