From what I read on Redmond Pie by Musclenerd it is all going to depend on Apple and when they decide to issue a base band that is higher than the 6.15 as with the newer boot roms they will not flash to a lower base band it has to be higher than the current base band. That is one of the major risks of flashing the iPad base band. It may never happen or it could happen shortly. Though my assumption would be that we may not see an iPhone base band higher than the 6.15.
So far they have not said anything but it does not look like it will happen anytime soon if ever. They would have to change the baseband number of the iPhone and I do not see that happening any time soon. I am not sure if they will ever have a baseband that is high enough to be able to change it.
