Not really answers but for those interested there is a fair amount of information in the planning document (pdf) available here:
http://www.sheffield.gov.uk/EasySite/lib/serveDocument.asp?doc=47470&pgid=64979
Then a bit more here:
http://planningdocs.sheffield.gov.uk/WAM/findCaseFile.do?appType=DC&appNumber=06/00846/OUT
I doubt there will be a supermarket on that site as I know the council are wanting a big superstore on the Chaucer School site further out on Halifax Road. That will be where Tesco et al want to go.
Can't find the links to that off hand but there is a little bit here:
http://www.pxforum.net/Building/index.html
Anyway, I'm sure it will all become clear by next year....