If Palpatine could come back from exploding, he is firmly in ‘The Master’ territory and there’s no hope of believing he’s ever gone for good.
I seem to recall that Lucas circa 2005 through TCW was adamant that Sith could not survive death. The one that appeared to Yoda was an apparition only.
And, yes, I know Lucas changes his mind on these things more often than his clothes. But, I hope he sticks with that idea and that JJ and company do, too.