I've always been fascinated by these sort of quasi sequels. Like I mentioned with La Casa... they were Evil Dead sequels in Italy, but had pretty much NOTHING to do with Raimi's films.
I'm still intent on getting them all. I believe 2 of the 3 have been released in the US with alternate titles. Though I'd love if they said Evil Dead 2, 3, 4 on the cover haha.
Similarly, there's already a Scream 4. And actually my copy of it does say Scream 4, though most of them that you see are called Last Stab. It's a cheapo indie flick by um Fred Olen Ray if I'm thinking straight? The director who did Murder Weapon and Leaches I think.
There's other examples -- many of which are from Italy. Zombi comes to mind.