If Alonso is waiting for Hamilton's future to be decided before he puts pen to anyone's paper he could be in for a long wait.
As I understand it (and I know contracts these days aren't worth a hill of beans as I have been reminded by so many of my fellow apex clippers in the past) Hamilton has one year left on his deal.
Mercedes are either in talks or about to enter talks on an extension so we can assume that Mercedes want their man to stay.
So, why would Hamilton consider leaving Mercedes now? One things for sure, the car will still be if not alone as the fastest by next season then certainly one of the fastest. He's got a team mate who can push him hard and yet he can still beat relatively comfortably on most Sundays and he's currently in a good place with his personal life both inside and outside of the team.
He's never really struck me as a money first type of bloke though of course, he's one of the sports biggest earners but that comes his way for a number of reasons, none the least now being a double world champion. Mercedes aren't short of a Euro or two so I'm sure that financial terms are not going to be factor.
So, when it boils down to it, I guess it all hinges on what Hamilton wants to do in the future. Does he want the seat at Ferrari that will surely open up at the end of next season? Will they want him? Will there be any other top spots open? It seems reasonable to suggest that his old seat at McLaren may be available for 2016.
I just can't see the gamble that not signing now and holding out for a year with all the surrounding speculation will bring so I would expect Hamilton to sign at least a 1 year extension with a mutual option for 1 more or something along those lines.
So, unless Alonso is hoping to fill Rosbergs seat and take on his old McLaren team mate all over again, I can't see him moving to Mercedes at all.