Today, in about 4h, an exchange will convert 2B Tether tokens TRC20 to ERC20.
You'll see multiple ERC20 authorisations, followed by TRC20 <=> ERC20 swaps and a final TRC20 burn.
As result of this operation the number of issued Tether tokens in circulation won't change.

Learn more about chain swaps ⬇
https://tether.to/explained-chain-swaps/