They have plenty of places to show the game from now on. PSX/Jump Festa this year, D23 February next year, E3 2018, TGS 2018, even PSX/Jump Festa in 2018 before the game comes out probably. I am sure they will skips some of these places..
Would still be nice to get some sort of trailer at this year's TGS but I am not expecting it at this point tbh.
About the next KH3 news Nomura said this (in July):
In regard to KH3, there's going to be another small intermission, but next time I'll be announcing more finer details about various systems, such as the battle and levelling systems
"Another" intermission similar in length to the one between E3 and D23 (slightly longer than that but not as long as past breaks between KH3 news) makes it seem like it could appear at TGS. Will be cool to get those finer details about battle and levelling systems, whenever it is next shown.