99% of open source projects fail within less than 10 years and are abandoned. The ones that don't have strong central control and financial backing by companies. Given the nature of the beast OpenJDK won't be around for long. It will be either absorbed by another group like Apache, become controlled by a competitor like IBM, or be overtaken by events and die a slow death in solitude as people move away from it towards other platforms.

Because the JDK is now open source, the question will always apply. In 10 years, the OpenJDK may not look much like it current incarnation, but it will still exist. Will Linux exist 10 years from now? Of course it will, but it will be better, faster, and more feature rich. The same is true for the OpenJDK. I believe the open nature of the JDK will drive its adoption to truly be everywhere in the future and people who don't like certain aspects of the JVM will alter it to fit their needs (such as invokedynamic, etc).