The number of people who will have the option of mailing in their ballots is more than EIGHT times the number in 2016. That means several hundred thousand people will have the option of voting by mail if they want or need to. See the data below.
For what it's worth, I've requested my mail-in ballot and I will use it if necessary. Right now I'm thinking I'll vote early, in person, on October 15, the first day of early voting. I am more than happy to risk my life to vote against Donald Fucking Trump.