The switch games Sword and Shield are going to be released this year. Too me it would make more sense if SW base set would be released around that time or a few weeks before. Since almost all the GEN9 pokemon have been finalized and created and the towns and items in the new region are at 85% completion. The set GG End will probably be our set before Sword&Shield Base set. We didn't get japan's Ultra Shiny GX set. So i dont think we will be recieving Remix Bout either.
We have historically gotten our sets coinciding with a new core game in February. This has been the case for years now, especially because of the November release dates every Pokemon game has gotten for the last five years. Japan generally gets the sets in December.
XY releases November 2013, Japan gets the set in December, and we get XY base in Feb. 2014
ORAS releases in November 2014, Japan gets Gaia Volcano/Tidal Storm in december, we get Primal Clash in Feb. 2015
Sun and Moon releases November, Japan got their SM base in Dec. 2016, we got SM Base in Feb. 2016.
USUM and Let's Go (Going by my view that Team Up is the Let's Go set) have followed suit, so knowing that Sword and Shield are coming out in late 2019, it's pretty much certain we're getting our Sword and Shield base set in Feb. 2020.
Also, you can't be certain we're not getting Remix Bout. We don't even know the kind of set it's going to be. I think Ultra Shiny could very well be either in promo products or its own set a la Shining Legends or Dragon Majesty, but we'll see.