And we don't know how it overall runs on switch yet either.
Nonetheless, if it is ue4, it is always possible and not surprising. It's not easy of course but it's alot easier than porting a non ue4 game.
Anyways DQ11 is ue4 and I'd argue that would be more difficult. Hellblade is a very linear experience.
I honestly think you are overselling what this port means.
DQ11 is open world and does run at a lower res on PS4 than Hellblade, it's true. On the other hand a cartoon art style tends to give the dev more leeway to make trimmings without it being quite as noticeable. And yeah, as I prefaced in the OP, this is speaking theoretically, if Hellblade turns out okay.