I'm not 100% sure, but you should still be able to find wild pet in the Vale come 5.4. There are still areas that haven't been ravaged (spoilers) yet, and since the wild pets can spawn in multiple places, at least a few of those areas should be safe.
Feel free to browse through Perks N Peeves, my vanity pet collecting blog!
The only ones I'd be worried about are Gilded Moth, which have very specific spawn points, all of which are in the affected area. I'm sure if anything does go wrong, Blizz will fix them in a later patch, but I'm glad I've got mine already anyway.