Good point Incognito, they do pass around slips and pressure people to make promises as to future donations and then to pay what they vow. They already have congregations on that everlasting mortgage plan.
I don't see them ever going to a straight tithe model of a certain percentage, but they'll just do what they do and be underhanded in the process the whole way. When you have 8,000,000 brain dead followers that you've manipulated into following your direction, you can get what you want.