The user base would just stop using MySQL and wait a few years for the dust to settle and see if a fork with a reliable management and reliable support structure emerges. It's as simple as that, the savings in using a free database are not worth the risk of betting on the wrong horse.
That's what the MySQL name means today: reliable project. No-risk choice. And not reliable because the code is good, reliable because of market acceptance, and number of concurring reports it works in the field.
Seeing the number of vultures circling MySQL now that Oracle is likely to get its hands on it, the chances for a single fork to emerge quickly are very low. Everyone is going to launch its own fork, and fight for the free database crown with Oracle laughing on the sidelines. (see how long it took for Centos to emerge as the "free" whitebox RHEL clone, how many promising projects went nowhere, and they were not aggressively fighting each other for mindshare).
Corporate market hates choices. Winner takes all. Oracle, RHEL, Ubuntu, are all example where a single actor cashed on customer unwillingness to choose between multiple similar choices. Brand is a very strong factor, more than code quality.