The F20/F21 hatch will run the usual ~7-7.5 years with a LCI after aprox. 3-3.5 years.
That means that the current 1 Series will run until ~end of 2018 / beginning of 2019.
Until then the 1 Series hatch will NOT switch to FWD obviously.
The next 1 Series (F46) on the other hand will run on the new UKL plattform which will be used by the grown Mini Cooper too and I guess you know what that means regardign FWD.
But for now: No worries until ~2019.