I'd say PewDiePie is retiring for a multitude of reasons, including general boredom and disillusionment, and if he does want to go back to making YouTube videos again, this is a smart move on his part. It gives him time to relax and recharge his batteries and given how we've had three seemingly back-to-back YouTube crackdowns, he can keep his head down and avoid the worst of it while still going out on top.
PewDiePie is the most successful of the old-school YouTubers and is probably going to go down in history as the only one whose story has a happy ending as opposed to either ending in disgrace like Onision or fading into complete obscurity like most YouTube e-celebs.
It's also obvious that YouTube is getting increasingly draconian and corporate in the lead-up to the 2020 Election and if Trump wins 2020, then Google will have to either relax their censorship policies (since they would obviously have failed) or YouTube ends up in the same grave as MySpace, YTMND, LiveJournal, and countless other hallmarks of Web 1.5 culture
If PewDiePie doesn't return after the election, then he's probably retired for good. Either way, he's making a wise choice with this and I wish him the best.