As I mentioned earlier, only three Atlantic hurricane seasons other than this one have recorded more than one Category 5 storm. Those seasons are 1960 (Donna, Ethel), 1961 (Cleo, Hattie), and 2005 (Emily, Katrina, Rita, Wilma). But here's what makes 2007 distinct: Each of the year's first two storms to reach hurricane strength have also reached Category 5 hurricane strength. You certainly don't see such a phenomenon with any of these other years.
I'm not sure exactly what to make of this particular record, but it seems unlikely to be equaled any time soon.
If storm intensity is due to warmer water, and the oceans are indeed getting warmer, wouldn't it be increasingly likely to have multiple cat 5 storms, earlier in the season?
Maybe, but it's still just hard to get a Category 5--all the conditions have to be right. You can't hit much land along the way, and so forth, or the storm won't get there.