The next revision of Sun's Java will have The Apache Foundation's Geronimo database incorporated. The link above will take you to a quick and easy read that will tell you a lot about where Java is headed.
No one posits Java as a replacement for AJAX or .NET, but it does have it's place and many developers prefer to work in it whenever it is suitable. Choosing the tools to do a given program in is as much dependent upon what the programmer knows as the suitability of the tools chosen. Java sees a tremendous market share in custom applications developed within and for an organization. The addition of a database can only strengthen this position.