I think SF^3 is more than just an UI layer, isn't? And isn't Qt primarily about the applications and UI layer, and not so much about the deeper level OS stuff (sorry for using layman, probably wrong terminology
). I may quite well be completely wrong. 
So, again, assuming I have at least a crumble of that right, I think the work done on SF^3 is likely to make a contribution to the SF^4 as well. In other words, the two teams (if there are two completely separate teams...) are not building completely unrelated, competing products. The OS part (as opposed to the UI part) SF^3 is the foundation on which the SF^4 is built. And I would be surprised if at least some UI parts of SF^3 would not repeated in SF^4 (even if implemented throught Qt in SF^4).


So, again, assuming I have at least a crumble of that right, I think the work done on SF^3 is likely to make a contribution to the SF^4 as well. In other words, the two teams (if there are two completely separate teams...) are not building completely unrelated, competing products. The OS part (as opposed to the UI part) SF^3 is the foundation on which the SF^4 is built. And I would be surprised if at least some UI parts of SF^3 would not repeated in SF^4 (even if implemented throught Qt in SF^4).