Who could be more interested in that installed base than Oracle? Although MySQL is a poor competitor, it would make an excellent complement to Oracle's existing database business. In fact, I'd say Oracle tipped its hand in 2005 when it acquired Innobase, makers of the leading transactional storage engine for MySQL.
MySQL's user base sits largely at what you might describe as the low end of the database market: Web sites, departmental servers, and single-use installations, for example. That's a niche that has been slipping through Oracle's fingers as its own database has grown in sophistication, complexity, and cost. By acquiring Sun, Oracle would be able to offer its customers a popular, well-recognized entry-level database, with an implicit upgrade path to Oracle's proprietary product as those customers' needs grow.
Oracle would be well served
Sun's other assets might seem like a poor fit for Oracle at first, but maybe not. One of the major complaints about a possible IBM/Sun merger was that it would leave the fate of Solaris up in the air. IBM already has AIX to worry about, and despite its heavy reliance on Linux, it has always preferred to partner with others rather than maintain a Linux distribution of its own. Oracle, on the other hand, already supports and manages a Linux distribution, and given the long history of Oracle databases on Solaris servers, it might actually see owning Solaris as an asset.
Among Solaris' most ballyhooed features is the ZFS filesystem -- which, according to the InfoWorld Test Center, "far surpasses anything available now on any platform" in terms of flexibility and scalability. Another is DTrace, a debugging feature that can be used to tune system performance. These kinds of features are just the things to appeal to performance-minded Oracle DBAs who want to manage their databases with minimal headaches.