Yes, I've been thinking of proposing this as part of our 4.6 effort, plans for which will start developing shortly (keep tuned, folks).
Traditionally we've supported "Version N and N-1" where "N" is the current version. PG 7.3 is going to start rolling out in at least preliminary form in September making it "N", apparently, so requiring PG 7.2 as a base while also working to make sure we work with whatever new incompatibilities the PG gifts us in PG 7.3 sounds like the right strategy to me.
Trying to make things work with PG 7.1, 7.2 *and* 7.3 sounds unjustifiably complex to me.
