I think learning GH1 is probably the best way to go if you want to start using GH2 on release day
I agree GH2 will bring several changes and a ton of new stuff, but the basic structure, data-flow and data manipulation will generally be on the same page
I truly think that despite the differences (that you can already familliarize with, on the WIP of Rhino8 + GH2) being fluent with GH1 will not “harm” the transition to GH2
