I'm going all applied and physical.
In parallel I'm going to do M820 (on my own, not officially with the OU) and study physics, particularly quantum mechanics, a bit of electromagnetism, and relativity. I've done all the maths to enable me to do this now. I've previously covered vector calculus which is required for electromagnetism, and this year I've covered differential geometry in a fairly abstract way, such that the way it's presented for general relativity seems pretty easy. M820 will cover Lagrangian formalism, and once I've done that I'll go back to my M827 text and re-read the bit about Lagrangians and Hamiltonians in the setting of a differentiable manifold.
All this stems from buying Roger Penrose's 'Road to Reality' tome, which I foolishly thought I could just read and then know everything. It's taken me 5 years of reasonably intense mathematical studying to get to the point where most of it makes sense, although I've still got a long way to go.
Year after that? Probably start working on my proof of the Riemann hypothesis