My bass teacher basically said that he'd taken me as far as he could with bass guitar, and being the jazz and soul fiend that he is he decided to start me on double bass (this was two years ago). Bless 'im lol I love the guy. Really talented bloke, if anyone lives in Oxfordshire and wants lessons I can give you his deets.
I reckon you should go for lessons mate, it manages to be an entirely different beast to the bass guitar, yet somehow oddly manages to make you feel at home. You won't regret it. While I play bass guitar more than double bass, it's still shummat I definitely won't be giving up in the near future.
My 2 cents