That is a worry I have, but on the other hand, more pro RTR brands out there is more opportunities to win over customers.
I had a galago ultrapro 10 years ago. Loved it, loved system 76's support for it (they shipped everyone a replacement keyboard at no cost simply because they weren't happy with the one it launched with). The only part I didn't like was the plastic body which saw a lot of wear and tear. But the laptop is still working fine.
Now I have a framework. The first touchpad on mine had issues. Wasn't registering clicks unless I pressed really hard. They shipped me a replacement, I swapped it out myself and shipped them back the defective one at no cost to me.
I wish both companies the best, but yeah I do hope there is enough business out there for them both.
Anecdotal, but my couple-years-ago work laptop was a System76 and my recent work laptop is a Framework. Both are running the same flavor of Linux and being used for the same things, I just decided that I liked the Framework's hardware much better (and that Linux was supported adequately on the Framework).
System76 support was very good, but the build quality of the Framework is definitely better (to say nothing of all the very exciting upgradeable bits)