If that happens it is pretty safe to predict that nginx will be forked immediately. Once it gets forked it can get community support without anyone worrying that they are supporting a paid version for free, and the enterprise people will have absolutely no control over features. Mysql got forked. And if you say that the mysql forks do not get sufficient community support (actually I do not know if that is the case) the reason is more likely the presence of a better sexier alternative (postgre) than anything to do with Oracle.

It is very hard to lock down free software if it is something popular or needed.