I'll be honest, real life is taking priority at the moment (and will for some time), and as I don't plan to upgrade my own site to XF2, there isn't an overwhelming urge to rewrite the add-on for XF2.
If and when I do, it's going to require a radical rethink as a lot of the functionality can now be achieved with built in XF code (widget positions and home page, for example).
So the first step would be looking at the existing feature set and deciding what to carry over and what to drop.
It may just be better to revert to pure featured thread functionality as it was originally, dropping the portal bit, as that can be achieved natively now.