I'm not convinced. Virtually everybody who has a 7-shot 686 or 8-shot 627 has a 6-shot revolver laying around somewhere. And for those who don't, I think most would agree that if you can afford to shoot USPSA, you can afford to acquire a 625 or 610.
My initial inclination was that it wouldn't hurt anything to change the rule, but then it occurred to me that you will occasionally see a stage where it would be well worth the procedural penalty to take one extra shot.
On the other hand, shooting a 7-shot or 8-shot .38/.357 is never going to be the best choice in USPSA anyway.
We've pretty much talked this issue to death over the years--when we had a poll on what guns should be allowed in USPSA Revolver Division, there was an overwhelming consensus to keep it six rounds between reloads, and no comped or ported barrels.