If you're worried about a rug pull, you should be. Not because Tailscale is shady, but because that's just how VC-funded infrastructure works. The free tier exists to build lock-in, not out of generosity. Headscale exists but honestly it's a pain to run compared to just paying Tailscale $18/user. The real answer is: if it's critical infrastructure, you should be running Wireguard directly and owning the coordination layer yourself. Everything else is renting convenience.
It happened to others but there are also some very good examples like Veeam community edition which, IMO, is the best backup software. They had lots of discussions and even pressure from management to terminated, but the numbers made a lot of sense and they kept it. Tailscale is in disadvantage here because they are in a very crowded market and it will be very easy to slip into one corner and let way for others like netbird, netmaker, nebula(?), wireguard (like u said), etc.