GTA is wholly unique in that it isn't impacted by the industry at large, and the things that would sink or dent other projects has little to no effect on the series and its sales. As someone mentioned, the delay will likely result in even higher sales, this is a series that generations talk about (and buy en masse). 

I know that I've lost interest. Could change in a year, but yeah. The steam has been completely let out of the bag.

It will impact launch sales in terms of helping GTA6 sell more, as the hardware install base will be much larger in November, with the holiday boost coming into play.

We may be looking at the PS5 setting a new holiday record for hardware sold with GTA6 though.

If trailer views are worth going off of, the numbers are markedly sluggish for the most recent trailer compared to the first. Maybe nothing significant but could be an indicator of a drop in interest. Alternatively, doing a reveal three years before launch can sometimes really pay off, as that means more time for word-of-mouth to spread the significance of this game. Case-and-point: Zelda BotW & TotK.

I know from my personal experience that the longer a game is revealed without a release, the more likely I am to hear about it, become interested, and maybe jump on at launch. Though this also can sometimes lead to an adverse effect of my interest is piqued, the game has released, and I subsequently push the game out of my thoughts b/c I don’t want to deal with the burden of waiting.

If anything, it'll probably make it sell more.

Would it sell even more with chocobos on it?

As mentioned it'll help it have a bigger launch due to a bigger PS5 install base. The PC version changing to be day and date would have a huge impact but as best  that version might release closer to the console version compared to before. To get morbid a way it'll technically impact sales is a tiny portion of people who would've bought it in May will die or lose the ability to play video games before November next year but that'll be counteracted by more people being able to play it. Long term though the impact will be negligible other than it somewhat lowering how much it'll sell on the current consoles due to the next gen ones being closer.

The people who've lost interest to buy the game at or near launch are a minority, I feel.
I don't see any way the launch sales are negatively impacted, and the lifetime sales probably won't be either.
GTA is pretty much unrivaled in the AAA space and most of gaming as a whole.

Not even a little bit

No but definetly the PS5 which isn't gonna be selling as much this year as I would have thought.