It does seem that Cubase has officially abandoned W7 to a degree with new update to C10.5. 10.5 is only supporting W10. That does not mean it won't work with W7, but I am not going there because of the statement and what members were saying on the Steinberg forum.
If it not broke, I don't find the need to fix it...
From every upgrade from Cubase 4 til now, all old projects have opened. I have had no issue myself. The leap from 32 to 64-bit software caused many problems, but that is a different story altogether.