In short: ~zygaN is the thing we can increment. We should KEEP and perhaps change the name to ~lava (but this has to be coordinated as ~lava < ~zyga.
There are three possible scenarios which this system correctly handles:
Right, but we can make that change anytime the upstream version gets bumped. So if it has an upstream version component that gets bumped, then feel free to change over to the ~lava designation as soon as you make a release that bumps the upstream version. Otherwise, if it's a component that uses YYYY.MM only, then we will wait until the 2011.07 release later this month to switch.