I don't see how or why they'd show us footage or a teaser for a game thats a minimum 3 years away after FF7R releases.
Three years seems kind of long. You can't forget that they'll likely be able to move on to & develop Part 2 much more efficiently (and have even said so themselves, that that's what they expect) than how long they took with Part 1, and that they can have some early work done on Part 2 even before the release of Part 1, as some of the workforce is freed up from Part 1. I also don't believe they have NOTHING figured out about the subsequent parts. They might not know how large this whole thing will end up being but I'm sure they have some story written, concept artwork done etc. that will speed up moving on with the development of Part 2.
They also have a seemingly strong base for gameplay to build the sequel on (vs. having to scrap and iterate on it for a while until they find something they find worth going forward with), they have their development studio set up that works exclusively on FFVII Remake, they should have the development pipeline fairly well figured out at this point and there's some reusable asset-work (tons of story-relevant characters they can use as is, possibly locations if there are some flashbacks or such in Part 1 that use locations outside Midgar, they can also do some colour/skin-swap enemies like Ice Bombs to pad out content without having to create something entirely from scratch).
If SQEX can do massive expansions to FFXIV every two years (while also pushing fairly meaningful amounts of new content periodically between those larger expansions), I don't think ~2 years between FFVIIR parts is totally impossible assuming they don't try to reinvent the wheel with each part.