I think whatever happens there must be consistency. Since Contador and Landis lost their titles and had them handed over to Schleck and Pereiro, if Armstrong is proven guilty of doping to a TdF win then the UCI must also hand over his wins to the second place person, unless that person too is proven to have doped in that TdF. They must either hand Armstrong's titles over to the runners-up, or they give Landis and Contador their titles back.
This means that if Ullrich did indeed only start doping after 2005 (yes, IF) he must retroactively be awarded Riis' 1996 title, as well as Armstrong's 2000,2001 & 2003 titles. Since there is also Basso's admission that he "intended" to dope in 2005, and some evidence Pantani doped in 1998, Ullrich might also get those titles too.
Of course this won't happen, but as a longtime fan of the long suffering Jan Ullrich, it would be sensationally delicious irony to see him retroactively become the first 7-time Tour de France champion!