The problem with that argument is that the absorption of East Germany into West Germany was only going to happen over the USSR's cold dead corpse or at least it's end-stage coma, by which time Poland would almost certainly be lost too and the problem would be a Polish one, not a Soviet/Russian one - as indeed turned out in practice. However, as WM points out, most folk would not be thinking about this in such objective detail....The risk of Ostdeutschland is that it could always be absorbed back into Westdeutschland, so any concessions that the Soviet Union will make towards it could eventually end up benefitting Westdeutschland.
Interestingly in this context, am I right in thinking that the 1990 German–Polish Border Treaty was the first time since the war that Germany formally and explicitly renounced its territorial claims to any parts of present-day Poland and finalised the Oder-Neisse line as the boundary? This presumably was on top of the more general amendments to the German constitution in the run-up to unification, that limited Germany to present-day territories and thus made her no longer open to further expansion into former eastern territories that were now within the borders of other states (Poland, Russia and Lithuania). This, presumably, implies that prior to 1990 Germany was open to expansion eastwards?