Rick: Don't they have sub-air under all the greens? If that is correct, then it would take a long time to lose firm greens. Also, because the site is so sloped, it drains very well, and so I think in total it would take a lot of rain in a short period, but recovery would be relatively quick.
Provided that nothing is changed form the last couple of years, Augusta will be a good, test of the new groove condition. Of course, it is only one test. so it will not be conclusive. The USGA clearly stated that the groove change is an effort to bring back accuracy (fairways hit) as a primary function of scoring, by bringing back the spector of "fliers" from the intermediate rough. Since this is the only type of rough Augusta maintains, we should have lots of opportunity to witness this phenomena, especially if wet conditions prevail. All of that, of course, is contingent on whether green conditions are similar to the past few years, which would be the best years with which to compare.