I cant see lewis leaving where he was essentially born and bred for DBR.
Although mclaren do need a sort out behind the scenes.
You think Hamilton will sacrifice his future career and winning potential to sit out his days in a team which cannot deliver a decent car?
If Hamilton does do as you suggest, he will probably be one of the first (top) F1 drivers in the last few decades, to sit out their entire career in a lesser team, simply for the sake of loyalty.
If you go back through the ages: MSc, Alonso, Senna, Mansell, Prost, Piquet (I could go on)...they have all switched teams on a regular basis according to whichever team would offer them the best deal (money or race/title winning opportunity).
If McLaren keep churning out cars which are about 0.5s/lap of the pace, Hamilton will have no choice but to move teams.
EDIT: come to think of it, can you name me even one driver, who is considered top class, who has stayed in a team (for loyalty), while they continued to manufacture lesser cars? I can only think of Button, though in his case, there may have been other reasons for him to stay at Honda. Also, Button was never being courted by the team with the fastest car (at the time Ferrari and Renault).