I've been told that many men have been excommunicated so that the excommunicator can take the excommunicated's wives.
If you're talking about the Church of Jesus Christ of Latter-Day Saints, I think you've been told wrong - certainly, at least, in this century.
If you're talking about one of the offshoot churches that still practices D&C 132 polygamy, then you're likely right.
But not the LDS.