According to this article, it seems to be a possibility as both AA and B6 CEOs haven't ruled out that possibility and it seems several OW carriers have "expressed their desire to speak to JetBlue."
Oneworld Eyeing JetBlue Links
http://bit.ly/cY9wn4
Looks like anything is possible in this hectic aviation era. Wow, I'd never would've thought it'd be a considerable option. AS' entry into OW would've been plausible but B6?
OTOH, bringing in B6 into a more cooperative codeshare would bring certain benefits as they do have several intra-West coast routes (SEA, PDX, SLC, SMF and SFO) that could be plugged in by OW, albeit many of those are to LGB instead of LAX.