I am really hoping that Game Freak takes a cue from this for Pokemon 2019, especially since (after the ComG first day preorders) I am not expecting Pokemon Let’s Go to sell as well as the core games (in fact now I think it will do rather poorly) nor am I expecting it to review well.
You're jumping the gun on Let's Go. I don't think it will do as well as the generational new games (X/Y, Sun/Moon) but I do think it will fall in line with the non-generational entries (third versions, sequels). So 5 to 10 million. Probably what they're expecting honestly.
They've already said the visuals and design of the next gen will continue the stylistic and design paths the last generation left off on. I don't think it will look exactly like this though. They'll lean more into the vibrant colors of Pokemon's setting. I expect something comparable to that 2011 Yokai footage. Though featuring more modern features in rendering, which we are already seeing a bit of in Let's Go despite its throwback look.