Though, at this point, I doubt it will happen.
My issue is that I think Sprint is going to die anyway. They don't have the customer base, or the network to really get new customers. To make subscriber numbers look better, they've been basically giving away service (I am currently on a free Sprint line, my second year, though I'll be cancelling soon when it is no longer free).
T-Mobile needs spectrum to improve service, particularly to really do 5G, and Sprint will give them that. If they don't merge, I believe Verizon and AT&T will end up buying most of Sprint's spectrum when they fail. To me the issue isn't going from 4 carriers to 3, the issue will be having 2 big carriers and a weak carrier with half the subscribers (and far less money) vs. having three carriers that are on more of an equal basis.