Skyteam Chairman Leo van Wijk gave an interview in which he discusses mileage upgrades coming to Skyteam, presumably much along the lines offered by most Star Alliance airlines (United being a notable exception).
[W]e will start a mileage upgrade program, where you can have upgrades from one carrier to the other. That will be available as of summer next year, but that requires also that we have a more coordinated fare structure. Otherwise, it’s difficult to implement. …
In principle, that will be a program that will not only be available in the North Atlantic, but we will start on the North Atlantic. We will test it in the fall of this year between the U.S. and the U.K. and France first. Then we will roll it out in the course of 2009, in principle, among all the SkyTeam carriers that can participate, because it does require certain IT functionality that is not available for all SkyTeam carriers. But the majority of the major carriers will be ready by that time to implement it, and not only on the North Atlantic.
Presumably these cross-alliance upgrades will be restricted to close to full fare tickets, and won’t be easy to secure (just try upgrading a Delta or Northwest transatlantic flight with their own miles…). Nonetheless, big progress it seems.