Making the core or traditional Pokemon game next year, gives them more time to work on it.
The point is, wording aside, the are clearly making a distinction between this title and the title that is coming next year. They didn't feel the need to make such a distinction with the other main titles.
Speaking of wording, “core series” and "main series" may also have distinction now, but I'm not sure.
Well of course they made a distinction, they changed the formula and they need to cover bases.
So here is what happens next, this game comes out and people buy it.
If the game sells well, very well, then you can expect a Gen 8 Go Intergrated title. If the game sells terribly, then we can expect the old formula to return.
They had to try something. If we look at sales, we see Gen 1, with 60million sales, then we see Sun / Moon with 24m sales, if we look down the line it is a steady but sure sales decline (with the Exception of X/Y).
Pokemon had to make a change, and try to get fresh meat in, but they had to be careful, they had to do it in a way that doesn't destroy their existing fan base. This game is a test, they are not sure how it will work out, and the only way to know is try. All they know is Go was a sensation, and they seen the light.
So mark my words, if Let's Go beats Sun and Moon in sales, this will be the future. They are a business, a few peoples wants are irrelevant to them. Speak with sales, if you don't want this to be the future, do not buy it.
If there is online, then that's a test too. I know they said VGC will stay on 3ds, sales can change that. I know it's the 151, DLC can change that. Maybe they are paying attention and thinking hmm, we have always been the smart ones, by selling multiple copies. What if we can sell multiple copies, and then for each copy a 30 dollar DLC or 3, of which is game specific, so you will need the DLCs for each version you buy.