I agree 100%. Next years standard sized iPhone will just be an "s" version of this years iPhone X. For the iPhone Plus: Using the iPhone X design, they can easily fit a Galaxy Note sized screen (or larger) within the footprint of the current iPhone 8 Plus. I also agree that Apple will probably do away with numbers and just call it iPhone. After all, now that we have an iPhone X (10) should we really expect Apple to release an iPhone 9? That being said, I do think Apple will keep an updated 4.7" iPhone in the lineup just for people who want a smaller screen.
In reality, this years iPhone X is kind of like a beta test for next year. I think the only thing that could hold back the iPhone X design from becoming the new standard is price... If Apple plans to sell the 5.8" as their new standard sized iPhone, they will have to get the price down to $799 or lower so the Plus model can take the $999 spot.
If they can't get the manufacturing cost down fast enough, I think it's possible that we may see an iPhone 8S and iPhone 8S Plus in 2018 (along with a larger version of the iPhone X) with 2019 being the year that the iPhone X design becomes the new standard.
Either way, it will be interesting to see how this progresses. Too bad we have to wait until November to get our hands on the X.