When Starship starts launching customer satellites, it's possible that even the price for customers would be cheap enough to launch and maintain a LEO constellation. But competing requires massive innovation in cheap and fast production of satellites which are very energy efficient and highly capable. Especially, the technology for starshield protecting against cyber warfare in space and the direct to cell capability. This would be the main reason for not emerging a viable competitor for some time. SpaceX has innovation advantage in the satellites, manufacturing, dishes, base stations, software apart from the launch capability.