UPDATED 11/5
As things stand right now...
61 Cubs minor leaguers are eligible for selection in the December 2021 MLB Rule 5 Draft, and 43 Cubs minor leaguers (27 post-2021 6YFA and 16 2021 second-contract players) are eligible to be declared MLB Rule 9 (formerly known as MLB Rule 55) minor league free-agents at 5 PM Eastern on the 5th day after the final game of the 2021 World Series (or at 5 PM Eastern on October 15th if the 2021 World Series is cancelled).
In addition, OF Nick Martini, RHP Adrian Sampson, RHP Kohl Stewart, and OF Trayce Thompson have Article XX-D rights, and can elect free-agency after being outrighted.