I think that means no iOS development so if you need that you need a real Mac
Third-party app stores and outright website-based app distribution are coming next year anyway.
It'd be rather similar to the situation with Docker, where Xcode and the simulators would run markedly better on macOS than on other platforms due to fewer layers being necessary. Developing for iOS on Windows or Linux would technically be possible but it wouldn't be very pleasant.
There may be ways to get around this but I don't of any.