I think the chances of Jenson staying are pretty slim. Beating your team mate while being on something like 1/3rd of Alonso's salary and your team now want to not give you the promised salary increase for the next year? Pretty bitter pill to swallow that.
Alonso being paid 25mil+ to drive this crap bucket, he's getting 8mil, promised 12mil next year but Mclaren don't want to pay it because the car sucks and it's not worth paying drivers that much to be at the back. This as they lose sponsors left right and centre over the past 2 years with more to follow at the end of this season.
He doesn't need the money now, he can get a more competitive driver in either a different series or maybe a different car though with limited options for 2016 now. He could go Haas I guess, Ferrari engine will offer a better drive than a damn Mclaren for next year I'd be almost certain. Yet to be seen exactly what Haas's real intentions are, the next Manor/Caterham or coming in at Sauber/TR level with the intention of investing and improving? Renault/Lotus potentially. Or take a year out, try another series and look for a drive in 2017 with probably a few seats opening up.