This would obviously be a win-win situation for both the developer and the user. But this would be beneficial for Nokia as well, because:
1) It'd provide Nokia with hard data based on sales and user feedback on which platform performs better in real-world scenarios. Currently, the decision to drop Meego for WP platform is mostly based on "hopes and promises".
2) Having both platforms compete on even terms would also improve the overall Nokia experience on both platforms as this open and fair competition would motivate both the Microsoft and the Meego teams to do better.
So, why this wouldn't happen?