Who will be the GOP candidate for Veep when Trump dumps Pence off the ticket?

News reports are that Vice President Mike Pence is quietly getting his machinery in place to pick up the baton if and when Trump drops it and run for president in 2020.

Trump's not going to like this and he very well may dump Pence off the ticket.

https://www.nytimes.com/2018/05/14/us/politics/pence-trump-midterms.html

If so, who's he going to pick? Will accepting the VP nomination destroy that person's chances in 2024 if Trump loses re-election.?