Next gen of 1er will be FWD.
Developing FWD platform for current 1er only would be extremely expensive. So BMW had two choices: either to find a partner for sharing a FWD platform (eg. Fiat, PSA, Toyota, Hyundai etc) for 1er, or develop FWD platform in-house for BMW & MINI only ... and make it profitable with expanding the model portfolio of both MINI & BMW brands in FWD segment. For an expected profit margin at least 800k units of FWD cars should have been sold (right now 1er + X1 + all MINI models generate sales of a bit over 600k units).
And that's exactly what BMW is doing. Putting all BMW 1er & sub-1er models on FWD platform (except 2er coupe, cabrio & GC - which will still be RWD, and based on modular RWD platform), sharing the platform with MINI & at the same time expanding MINI product portfolio. So, 1er family (hatch, touring/GT, CST etc), X1/X2, sub-1er models, all MINI models (incl. Countryman Coupe, possible Countryman Cabrio, MINI "Spaceman" - a mini-van by MINI etc) all based on modular FWD "UKL" platform will definitely generate a sale of more than 800k units per year. An therefore the desired profit margin will be met.
Audi has VAG's "MQB" FWD platform - which is extremely profitable since lots of VW, Skoda, Seat & Audi models are based on it. So Audi profit margin is covered here. And this gives Audi a huge advantage over MB & BMW for at least one generation of compact models.
MB have developed current modular "MFA" platform on its own - initially for its A & B-class models. But the economies of scale doesn't work here since A & B do not generate enough sale for MFA platform to be profitable enough. Therefore MB's cooperation with Renault-Nissan: so I guess MFA platform will be offered to R-N for some of their models, boosting the profitability of MFA platform. Or perhaps in the future R-N & MB will develop a common FWD platform together for compact cars. Perhaps even for the next generation of A/B class already.