Hi Stefan!
PyData/Sparse is pretty far along, by January or so we should have a CSR/CSC replacement that is ND. It needs optimisation in a lot of cases but the API is compatible with NumPy and works pretty well already IMO.
PyData/Sparse is pretty much independent of any changes to scipy.sparse at this point. We build on top of NumPy, not scipy.sparse.
Feel free to use any or all of my code for sparray, although I think Ralf Gommers, Matthew Rocklin and others were of the opinion that the data structure should stay in PyData/Sparse and linear algebra and csgraph etc should go into SciPy.