What to do with Alpha lenses?

Thanks to all who replied.  Conflicting advice, yes, but each of you brought up interesting points.  I wouldn't have asked if I wasn't conflicted myself.

I think part of me is just curious about DSLR/SLT shooting and how it will compare to my experience with the NEX.  I'm just an enthusiastic amateur, and really the NEX-5N with the 18-200 zoom gives me results that satisfy my needs.  But I don't want to get bored with the hobby, and maybe a DSLR/SLT will open up some other photo opportunities for me where the NEX underperforms.  As long as I get a good deal on a used body, I can always get back out without much damage if I decide it's not for me afterall.