You will be perfectly able to use Win7 with 7th generation BUT further windows updates won't be downloaded on windows 7 / 8 / 8.1 because Windows wants people to move to Windows 10.
They say it's because compatibility problems but that's BS so, if you plan on getting 7th gen on Win7, take a good antimalware program since Windows one will be outdated soon.
This video explaina what I mean perfectly: