Metabones makes an EF-to-E adapter that brings all of the electronic features across except autofocus and some of the lens correction information. A full-featured adapter could happen, but you could lose out on an awful lot of shooting waiting for it.

Selecting lenses with an eye toward the future is a good idea, but the adapter's US$400 price tag makes the economics of upgrading to a SLR body sooner rather than later somewhat favorable. This is especially true if you'd like the full function of the lenses available and you don't already have a lot sunk into E-mount glass for your NEX. Bottom-of-the-line SLR bodies can be put on the road for US$500-700 depending on which one you buy.

As you've observed, Sony's shortcoming is that there isn't anywhere near as much of an ecosystem of E-mount lenses as there is for some of the better-known systems like Canon's EF and Nikon's F. If your needs aren't being met and you don't see them being met in the near future, it might be time to pull the rip cord and buy into another system. I ran into the same problem in 1994, switched systems and still occasionally use the first lens I bought then despite being several bodies removed.

Once you've bought into one of the major systems, the old saw that bodies are for Christmas and lenses are forever holds true. As long as the manufacturer doesn't change the lens mount, you get to take all of your lenses with you when you change to another body within the same system.