The star tracking feature would make me seriously consider skipping the R6 and saving up even longer to get the R5.
I can't see the star tracking to be that good at all. It could help of course, but by how much? Olympus makes one, right? Or at least was about to when they announced it a few months ago. Are they saying it would be hand held or tripod a must?
Astronomers use star trackers (as you might already know, since you're interested in the camera feature) that cost around $350, that mount onto tripods. Those are ones where you might be able to use up to a 200 mm lens. Usually with those trackers you'll be using with a lens around 10-80mm. Anything longer than about 200 and you'll need a telescope mount/tracker (my Sky-Watcher HEQ5 goes for around $1050 and is considered an entry level model). With the longer FL, you need to get a guide scope camera and scope (at least a $250 combo) to help track it even more. Often they are used with a laptop to control and always require some sort of polar alignment (or plate solving). Even with all that, and my entry level mount, people see all types of flaws compared to more expense equipment.
Plus, you need to track the objects for quite some time. Often hours, in order to take multiple exposures (sometime hundred or more) of precisely tracked photos to be stacked in software.
I think for casual snapshots of non-deep sky object , but rather night sky/skyline, it would look better than a regular camera and ok for some people. Canon Ra much better for the serious astrophotographer. I would much rather purchase the R6 with a $350 star tracker, than the R5 with the tracker feature built in. It would cost way less and work much better for any astro type photography. I think people are saying the R6 will be better for low light, making it better for night sky. But if there is more than just the added star tracker feature you'd want that doesn't come with the R6, then the R5 may still be your best bet.