Eeehh It's been a nearly decade long gap since the last Shrek, and in that time, the landscape has long changed. There's a lot a fifth film could potentially do.
The first film was basically a direct response to the Disney Renaissance. And assuming we've kinda just had a second age of that with the likes of Tangled, Frozen and the like, animated fairytales are kinda a big deal again. Think there's a lot Shrek 5 could potentially pull from there.
Heck, sequels and reboots have been a big thing, why not parody that with one of your own?
it's been 12+ years since the last outing. I think enough time has passed. I'm not asking for it to fully continue again, just at least Shrek 5 to see the ol friends again after a long while.
And hey, assuming **** in boots 2 just got glowing reviews, I'm sure if you get the sameish team, they could do Shrek 5 justice.