Well of course he’s not dead. I have some very important reasons why.
1. They didn’t show a body (On Tv and Movies if they don’t show a body your not dead)
2. He’s a main character.
3. He disappeared in a puff of white lights. Perfect excuse to say he got teleported somewhere. Also a good excuse to bring Pan back.
4. By undoing Storybrooke you have a chance to say that the events that took place never occurred thus brining back Rumple same way David was brought back when the curse was enacted.
5. Ratings. Rumple best alley right now are the studio execs who want to make a whole lot of money.