Oh dear - the Mormon church is shrinking! Not.
You want to see real mass resignations from the Mormon church? Implement within the church a policy of acceptance of gay married couples. Watch the dramatic resignations then! And I suspect the leaders know this.
As the church authorties noted in the above link, less than 4% of those resigning were active Mormons. That means over 96% of the resignations were inactive Mormons.
I note elsewhere in that same article it described the Mormon church as fast-growing, with 15,000,000 members. I'd presume that, like the JW organization, the bulk of the growth is in non-Western lands where the liberal thinking of the West is anathema.