What are your current lens collection and what are some of your needs?
The thing with Nikon mirrorless is that at least initially it will likely only be a supplementary system for many unless you're lucky enough to want exactly those lenses that Nikon release first. It will be many years before it will have the same depth and breadth of the F-mount lineup so it really depends on what lenses you want/need.
For versatility, the mirrorless will be better since the development announcement has also confirmed the F-mount adapter. How well it works remains to be seen and ultimately native lenses will still be better.
I think if your lens needs are the common bread and butter ranges eg. normal zooms, wide zooms, common focal length primes like 24/25/50/85mm then those will likely be filled quickly in the mirrorless mount. If you require longer telephotos or specialist primes like the 105/1.4, unless Nikon does a Sigma and re-uses existing optical formulas on the new mount, you might have to wait a long time.