As of 2013, there were more than 430,000 Latter-day Saint boys in the Boy Scouts, per The Salt Lake Tribune.
I attended training at Philmont where there were several very active Mormon leaders.
It will be interesting to see if the BSA units remain as active troops but under non Mormon Sponsoring institutions.
That is, any Church or group can take over as sponsoring institution of the troop and all the membership remain as is.