These things happen in phases. The side I dance with was like Great Western is now 6-7 years ago, with lots of young dancers - most of whom enthusiastic sons of older members. They'll soon find that the sons and daughters geographically disperse, some to lose interest, some to join other sides in their new location. Hammersmith in particular do quite well out of the fact that dancers of university age come to London and end up joining because it has a reputation for excellence/fun.

I don't think that there is any danger of Morris as a tradition dying out but there is every likelihood that some teams will find themselves with not enough dancers to perform regularly.

I agree with Joseph P above that 'trying too hard to recruit' is a turn off. The answer would seem to be to attract on the standard of dancing itself. Hammersmith/Great Western/Bedlams/Kingsmen are all wonderful teams with excellent musicians that train their dancers properly before letting them dance out in kit. As a result they look impressive and have people queueing up to join.