Nothing will happen to Java. Oracle's entire e-business suite (the primary money maker for Oracle, not their database) is built on java. Oracle has been using java for more than 5 years and is very heavily invested in it's success. This is the primary reason why Oracle buying Sun is a smart deal for Oracle.
As for MySQL, my guess is nothing much changes. Oracle gets, but does not really actively support, open source software. See, for example, the BerkeleyDB. It still exists as open source and is being enhanced. There is a small team working on BerkeleyDB.
Who know, maybe Oracle will let some of their database developers loose into the MySQL code and let them make vast improvements.