I have seen a lot of hopeless users that do not want to change to Win 10, thinking of what they will do after Win 7 becomes unsupported. This is the first reason to announce this project early, so hopefully bring them a brink of hope for their beloved OS.
The second reason was a bit in heat of the moment, as I was working on Win 10 on a project of mine and the system would progressively become more sluggish until I restart it. There are also another rare bugs from Win 8 that are still unfixed, as explorer.exe could suddenly crash itself into oblivion until you restart it from Task Manager and many more ... So I decided I had enough and became determined that I will ressurect the last real OS once it's officially dead.
The project will begin in Jan 2020, after the final update has been released by Microsoft, since my project will involve a lot of system files modifications and I wouldn't want a sudden new update to overwrite them.