Perhaps the wrong question was asked. How many will move to a group if it is formed? If there were on the order of 100 votes to move, I suspect that is about how many will move. How many does that leave behind? Perhaps just those interested actively will move and it doesn't make much difference.?
I suspect the Yahoo groups will be around for a long time and the gloom and doom is unfounded. Yahoo was bought for the traffic and I bet they they generate a good bit of the total.
73 - Mike WA8BXN