I love speculation as much as the next guy and as a marketing guy the random buzz that is generated is great and all but you guys could just ask the question to the company directly instead of speculating yanno....
Stage 3 w/ big turbos is coming. I have no ETA or specs however as development on the S55 big turbos is still pretty early on. We are also more heavily focused on closing out the N55 big turbo program that will be released here in the near future (working with the turbo vendor on the core program/issues at the moment but development is basically done) as well as swapping out the current/old N54 program over to the new vendor as well. The stage 3 / big turbo solution will carry the same BMW matching new car warranty and will also be designed to be emissions legal in all 50 states (probably not at launch as the paperwork process takes forever but nonetheless that is the plan).
The further intent down the line; and by the time the S55 big turbos come out it may come out concurrently, would be to offer a stage 4 / race map at the same time that would be designed to take full advantage of race fuel on the big turbo setup. A lot of warranty questions come up with that topic though which haven't been fully addressed yet.