Alonso will definitely leave McLaren for sure. Team that are rumored to be for him besides Wiliams are Reno and Mercedes. Dont know how he will be in Mercedes cuz he left McLaren last time due to fight with Lewis. This one is hard to back up, for other teams think that its very possible reason they have better engine and the car from current McLaren one. This is hard for Alonso seeing him so only cuz power unit when down twice in last two races, must say this is frustrating to the rooftop.
Still he announced that he will say after next race what he will do will he stay in Formula 1 or leave. It would be shame to see him leave but think he is also considering to go in INDY championship cuz he almost won INDY 500 he lead most of the race but engine blow up.