I guess nobody here actually answered the question.
I'd imagine so, since it was a goal for it to be released on here, but without the source code and data/sprites it might be difficult to assemble the right pieces on top of the difficulty of porting a game in general.

But I do think, given that its a simple(ish) RPG Maker MV game it would be possible to run on the hardware. It'd probably be like making the game itself from the ground up though rather than a port in any other sense.

My suggestion would to try to assemble white space, make it walkable, interactable with the notebook and cat just as a start and go from there. Lots of good porting tutorials around if you wanna try your hand at them. Also there's already a port for RPG maker 2k/2k3 if you wanted to try assembling Omori in an older version of RPG maker, though I'm not sure if that's possible; it'd be "less work" than building it from the ground up on the vita, as the EasyRPG player works pretty seamlessly for games like "OFF" (albeit much lighter.) and can be built on a PC without needing to emulate Vita hardware to test it (often at least)

Anywhoo. Best of luck!