Yes. Having a third competitor in the GPU space could disrupt prices. Right now Nvidia and AMD are easily able to ask almost whatever they want for high end GPUs. Unless someone comes along and says, no, you can have that performance for 30% less money.
A770 didn't quite make it this go around (which is a 16GB card for $400, under $300 if you get the 8GB card), but it is priced according to its performance, not features. If Battlemage or Celestial can do anywhere near the RTX4070 or RX6800 for $500 they will have a winner.
RX 6800 is there right now at $470 (After lowered pricing following the 4070 launch), and is what Nvidia could be doing with the RTX4070, but they choose to ask $600.
AMD chose to wait 6 months since the launch of the 7900XTX and 7900XT before launching any of the lesser cards (If we believe the June launch date). Nvidia has spaced out the 40 series more tightly at the high end (one card per month, but waited an additional 3 months for the 4070. (Though somewhat understandable, mobile 4080, desktop 4070 /Ti share a GPU, so they've really launched three products with that chip) AMD has launched all their mobile 7000 series parts with Navi 33, with the two desktop cards being Navi 31.
If the RX 7800 is reasonably priced, and there is no reason to suspect it will with the 7900 XT's $900 price, there is room for a disruptor. Though Intel looks to still be about a year out from their next launch.