Since the ubuntu conference where they discussed Rick Spencer's proposal, Mark Shuttleworth (the leader of ubuntu) has laid out a refinement in the proposal that he feels would be best to consider (based on the feedback they received)...I suspect they will probably go with this new plan instead...
Everything would basically remain as it is now, except the support on interim releases (6 month ones) would be reduced...And the Rolling Release will not be the mainstream ubuntu but rather remain "development branch" available to all who prefer a rolling release...ubuntu name and number would always stay the same (example 13.04 "raring ringtail") so that no upgrading would be needed..you just install and ROLL continuously from one ubuntu release to the next...
To answer skywolfblue's question: in a rolling release you just keep getting updates (you don't upgrade at all) and those updates contain changes to the various components of the distro, including newer software as well...
If they adopt Mark's refined proposal, it probably won't affect linux mint at all as i'd imagine that Clem would stick with the 6 month releases...though i suppose he could offer the optional rolling model from ubuntu's development base if he wanted to and assuming it would work with what he would want to add to it on his side...but perhaps that would be too difficult...(in which case you'd have to use ubuntu directly if you wanted the rolling release option they would offer)...
In a "Rolling Release" you receive updates every day which make changes, rather then waiting 6 months to do an "upgrade" so your system is always going through changes...
This is from the summary of his proposal:
Basically, the mentioned proposals would structure Ubuntu as:
Ubuntu LTS
Ubuntu Interim releases (between LTSes, supported 7 months)
rolling-release model for the Ubuntu development release (keeping a singular name, thus users are able to continuously use the development version without a traditional upgrade process)