Good luck? TSMC serving hundreds / thousands of fabless firms isn't a con per se. It helps amortize the obscene cost of R&D. What, is Rapidus going to recoup all that R&D in the years that 2nm is the leading edge?
No. Once 2nm is cheap enough, they'll likely find enormous profits by allowing more cost-sensitive firms to fabricate on 2nm. Some money is better than no money.
TL;DR: You don't build an apartment building and then when the building is old, you demolish it and start over. No, you reduce prices and get more customers.
It'll all depend on Rapidus' execution. If they can guarantee higher-quantity / higher-perf / lower-power, yeah, the world over will be pining to get fabbed there.
If not? Welcome to the world of "a few steps behind" TSMC, aka Intel & Samsung.