Release date (though that's looking too likely given xbox series x is releasing in November but if Sony opt for a December release (which I don't see happening), it would give xbox a potentially significant headstart.
Stock (though Sony are calling for a pretty large release)
Price (I could see this being a factor)
Hardware issues (launch consoles often come with their own flaws, if the PS5 has any major issues, it might turn people off until it's fixed)
(i don't have a better way to describe this but we do know both Sony and Microsoft are holding back on info, I personally don't know what they could reveal that could push them up like Halo did but it's worth noting at least).
At the sony event they showed PS5 games running on PS5s.
The same wasnt true for the xbox event.
I doubt theres hardware issues that'll pop up with the PS5.
Release date wont effect things much either, switch proved you can even release a console in say Q2, and in the end if anything its almost smarter to do so.
Stock shortages? again they put in more than 10m orders for the release window.
So basically apart from games, or price of the console, I dont much of anything could effect things now.
Lockheart is the only question mark, that might turn things around.
If lockheart is like 250$ and enough people that want a new gen, are fine with playing at 900p-1080p.... that might put on some pressure for sony.
Esp if the PS5 is priced on the higher end of things (instead of 499$ say 549$ or 599$).
Don't get me wrong, I still think the PS5 will definitely outsell the Xbox Series X but these are things that could impact the sales, most of which I already countered in my post.
Consoles are notorious for having issues at launch. We can all hope that everything works out but until it actually releases, you can't really say the system will release without issue.
Also, as you said, lockheart could be a factor as well.