I think there are two possible workarounds, I'm not sure if these work since I only use 09 versions and I don't have the newer iWork installed (this nagging was one of the reasons I uninstalled the newer versions).
1. Hide Pages/ Numbers in the App Store software update by right clicking (Control click with one button mouse) them and selecting "Hide update".
2. Install software such as Little Snitch and block Pages/Numbers connections.