As far as I know this is definately the last season. link
They may do a spin off thing with the interns, but as far as we know season 8 is the last. =]
This is the last series with the main cast. Zach Braff and Bill Lawrence were always leaving after this series but ABC were considering carrying it on without them. Then however Judy Reyes announced this was her last series and Niel Flinn got a part in a sitcom so was also leaving. Thus they decided to make this the last series and I am sure it will be missed. I think a story about the interns is on the table but i think it is highly unlikely that it will happen.