Microsoft wants to release a major update of NAV on a yearly basis. So indeed you can expect NAV 8 to be released by the end 2013/beginning 2014...
The code name for the next release is "Sicily" you can try to google for "Nav sicily" to get more information about it.
Anyway here is a recent blogpost about Sicily : saurav-nav.blogspot.nl/.../get-ready-for-new-version-of-nav-nav-8.html
Regards,