There is a confusion going on on some websites, but the answer is plain simple - there is only one box for use with Scratch Live - the SL1. You may have found the websites-stores that sell Scratch Live with 2nd edition control vinyl I suppose. That's the deal.
If I am wrong and there ARE secret works going on to develop an SL2, then sorry to ya'll :)
That would be my guess as well, you're seeing the 2nd edition control vinyl and thinking there's a second edition of SSL or SL-2. There isn't, just an updated, more refined, version of the control vinyl. So go buy SSL already! :)