From Canon T3i to Nex-6. Am I giving up some image quality?

Well, I can safely say my NEX-7 blows my T2i away!

But unlike you, I got the NEX in large part to work with prime lenses more - particularly my old Nikkors, most of which work wonderfully. (As do the two native primes I've splurged on - Sigma 30 and Sony/Zeiss 24.)

Sony's official e-mount road map does promise a "high performance standard [G] zoom" - I'd be surprised if that were to never materialize. I wouldn't be surprised if you had to wait until the end of next year, maybe longer.

In the meantime, the kit zoom might hold you over - folks have posted some pretty nice shots taken with it.