If I left WP, which I'm considering (not for lack of interest; just bored), I would go to Ubuntu Touch and/or Android with the Launcher8 theme installed. Ubuntu Touch looks amazing, all its missing are apps. Android, I can't stand certain aspects of it, but I love the openness of it. So, I'd probably run an Ubuntu Touch/Android (again, with the Launcher8 theme) dual boot. Covers the best of everything. Apps through Android (until UT gets the essentials), live tiles through an Android skin, and the pure incredibility of UT.
Slightly off-topic: Since UT is lacking in apps right now and will be for a long, long time once its actually launched, Canonical should really focus on getting convergence ready. Then whenever there's an app I need, I can just plug my phone into a KVM. I use my laptop a lot more than my WP anyway, so this would be perfect for me as a developer.