Oracle shouldn't care about the switchers
to MariaDB etc.. at least for a good long time, likely those were not paying Oracle customers anyway. The ones that really care about the open community etc also are not likely to be paying Oracle customers(now or any time in the future).
Obviously there's quite a bit of value in the MySQL brand which will keep the momentum going for some time.
It will be interesting to see the rate of innovation out of Oracle MySQL vs the community forks, given the resources Oracle seems to have put into MySQL.
What would perhaps get my attention is if the community folks ditched Oracle InnoDB in favor of something more open. Would be interesting to see how that might work out.