Bandai Namco never trusted the market is for AC titles. To be honest, who could blame them.
AC7 was the first title to outsell AC04 after almost 20 years! And I don't expect that to change with the next title.
I bet AC7 only exist due to the low cost it took to rework Infinity into UE4 and sell it in between other major releases.
Expect the skins to never stop, you can see how bad they wanted to make money out of this series with Infinity. Although if you consider how many nostalgia skins are left to give out, they are pretty much done with the recent drop of the AC5 skins, they just have the portable titles to milk now. This may mean they are ready to show off something new.
No clue when AC8 will come out but the delay is 100% caused by them trying to figure out how to get the VR to work well.