GH1 will be there in the next few years at least, as long as Rhino 6 and 7 are still used, probably for Rhino 8 as well. Probably GH1 will still be available later, why not?
My current plugin is planned to be developed in two years, no fear. In the core project I don’t even reference Grasshopper.dll and I have another project for the GH version. When GH2 comes out, I will make another wrap of my core. At the end my plugin it is a Rhino plugin, even though I’m GH first, since it depends on Rhinocommon.
It depends on what your plugin does, on how dependent you make it on Grasshopper. If it takes care of making geometry, using Rhinocommon, no problem, if it takes care of playing with the canvas, you won’t be able to migrate it. GH2 is written from scratch, so you shouldn’t expect any compatibility. Instead of making the logics inside the components, make them outside and call them from the components (besides you can also call them from scripting components and do unit tests in GH or even develop it over). Wrapping your plugin in GH, taking into account 5 types, 5 parameters and 30 components, with descriptions, icons, etc, shouldn’t take more than three days with the proper experience or a week, so for a half year or more project, it’s acceptable. I mean, if you develop the logic on the one hand and the GH wrap on the other, it’s worth doing it now.