There are forums for all kinds of singles players that are inactive - some are for guys barely in the top 100 or even 200 in a couple of cases. I think it should be looked at in a case-by-case manner, such as these threads. If even half the people who posted in this thread come to a forum for the Bryans, it will be a very active place
And also, there's no risk of them splitting up. Many of the doubles teams that are at the top don't play together for that long, but the Bryans do. They also play mixed doubles at some of the slams and Bob might try to jumpstart his singles career so I think there's special potential for a forum for them to be pretty active
