If Israel annexes the West Bank and Gaza, should Palestinians get the vote?

Yes, if Israel annexes an area currently populated by Palestinians, and that area becomes legally seen as part of Israel, those citizens should be seen as part of Israel too.....and that includes being allowed to vote.

Should? Absolutely. The only way Israel could morally justify taking over West Bank and Gaza would be for them to allow Palestinians to participate in the government. Unfortunately chances are that Israel will merely push further into Palestinian territory without annexation and try to avoid any real solution of the matter. It doesn't really help either that this is nearly a century long conflict in which neither side wishes to concede. In the end, Palestine will be Palestine and Israel wil be Israel, and they shall forever be at each other's throats.