In an upcoming fix to servers coming next Tuesday, Blizzard plans to make all battlegrounds 10v10. This mode is certainly much more popular than 15v15 and this can increase people's participation in rated Battlegrounds.
Let's see the full text from Blizzard:
[blue author = »Blizzard Entertainment» source = »http://eu.battle.net/wow/es/blog/1834024#blog»]
We are developing a live fix, intending to roll out next Tuesday, that will convert 15v15 rated battleground weeks to 10v10 weeks.
Taking a look at the engagement, we found that the 10v10 rated battleground weeks were much more successful than the 15v15 weeks. The difference in organization requirements and the popularity of the battlefield map have been major factors that have made the 10v10 weeks that much more active. By making this change and supporting the popular election we hope to further encourage players and teams to participate, as they will not have to wait for the next week or be rushed by having to gather 15 players to fulfill the requirement.
In the future, we also plan to adapt additional battleground maps to work in 10-player mode, so that there is a greater variety of maps available.
[/blue]