when can we expect a ubuntu 16.04 version of cuda? More general, how long after a major release of an operating system can we expect an update? Do you need help from the community?
The packages you can get from the official Ubuntu repositories integrate CUDA 7.5 very well with Ubuntu 16.04.
It may not be an nVidia-supported combination of distribution and CUDA release, but in my testing it worked just fine.
Expect a CUDA 8.0 release this summer (together with the Pascal consumer GPUs). I don’t know if Ubuntu 16.04 would be a supported OS for this release.