Yes, that's always good. I am just thinking about how many people would be made angry, if option to use native VFB was completely removed and there would be only CoronaVFB.
At least me ;) . Don't ever break any fallbacks. There are sometimes reasons (be it a plugin like vfb+ or deadline or backburner or pipeline dependent tools for the standard vfb or whatever) to use the Standard framebuffer.
If you always keep legacy, you may end up like Vray, or worse, like Mental Ray. There should be done clean up every once in a while, but result should never be worse than previous state. Here i am thinking just about removing possibility to select it in UI, but it would not be completely gone, so network rendering managers could still use it. Right now, it would make most sense to simply move the entire dropdown menu into devel/debug settings, and make some trigger which would activate it in case VFB+ is installed.
Of course this can only happen when there's nothing that native VFB can do but CoronaVFB not, which is not the case yet, but hopefully will be soon.