OpenSolaris was really useful and innovative, too. I am happy that ZFS and Dtrace found their way to Linux (though not without some issues), however, I would rather prefer the whole package.
In terms of scope OpenJDK would be comparable to Mozilla's mission. So even if Mozilla didn't grow to take it on, a similar sized org could. The point being open source specific Mozilla pattern orgs rather than private corps.
Oracle's pulling out would not be enough to kill the project. Mozilla could easily take it on.