It will probably not work. In fact, the driver API might work, but I have not yet updated to CUDA 5.0, and you should not rely on that.
I'm currently busy with some other tasks, e.g. the update of JOCL for OpenCL 1.2, but the update for CUDA 5.0 is already scheduled.
BTW: One aspect of the update of JOCL was an internal refactoring that should make the library a little bit more "agnostic" concerning the version underlying implementation. A similar concept could be applicable for JCuda. At the moment, there usually has to be a strict 1:1 correspondence of the CUDA version and the JCuda version, which is undesirable. It would be nice to have the possibility to use e.g. CUDA 5 with JCuda 0.4.2 or CUDA 4.0 with JCuda 0.4.2. However, for JCuda such a refactoring would be a considerable effort, and I'm not sure when I'll find the time to tackle this, although I see this as a very important task. It will probably not be part of the update for CUDA 5.0, but maybe of another 5.x version.