Yes and yes. It will be a collection of all the episodes with a "mini-overworld" where all the items will be usable as you unlock them. The earlier episodes will receive a remake as I'm improving the engine (and in the case of Episode III am changing how perspective and cliffs work).
It will be available here on Itch as well!
We're probably a good while out from the release though. If all goes as plans, at least, the later episodes shouldn't take so long to develop as III did.