I wouldn't be surprised if a digital-only PS4 launches as the Super Slim 1-3 years from now. I guess it depends on retail relationships because Sony could also just shrink things again with the next node shrink if digital-only would raise tensions with retail.
The portable is a whole different issue because you need a lot of different components to drop in price or become a reality if you want it to literally play PS4 games with no changes except resolution. Mobile tech still needs to mature to produce a chip that can run at PS4-levels with a >1 hour battery life, and flash memory's cost needs to drop to be able to support PS4-sized games both on carts and in internal storage. Nintendo did pretty well with their tech in Switch, so even taking into account cutting out all the Joy-Con cost, it's still a few years away before this would be feasible and at a price that people wouldn't laugh at. My guess is this will be reasonably possible around the time of the PS5, which seems a bit late.
Personally, I'd absolutely be down for a digital-only Super Slim if it means it's smaller, quieter, cooler, and using less power. I have a Switch but am not particularly interested in its hybrid aspects, so the portable is not for me.
EDIT: One interesting idea might be to launch the PS5 in two variants: a console variant that targets 4K and a portable variant that does 720p undocked/1080p docked. AMD is advertising Navi as scalable, and perhaps the gap between 4K and 720p/1080p would be enough to make an equivalent portable feasible in 2020.