Damned if you do, damned if you dont. I think that Rodon would likely accept the QO if offered. Maybe someone is willing to offer him 3/60 this off season (assuming the Sox havent made a similar offer). That said, if Rodon replicates this seasons results next year, he goes into free agency as a 30 year old with around 800 career innings with no draft pick compensation attached to him.
Not offering the QO would mean losing a 5.0 WAR pitcher for nothing. Going for Stroman, Ray, Scherzer, etc. would be much more expensive and long term proposition. I think there are serious questions about whether the Sox can depend on Kopech to make starts in 2022 and it seems exceedingly unlikely that Crochet will be a starter.
Making the wrong call on Rodon's health would be pretty catastrophic. The Sox now have some expensive players on the books in Abreu (19.6M), Lynn (18.5M), Grandal (18.2M), Keuchel (18M), Moncada (13.8M), and Hendricks (13.3M) all over the 10M threshold. The Sox also have an $16M option on Kimbrel to decide on. If the Sox pick up Kimbrel's option that puts them at $136M for Abreu, Lynn, Grandal, Keuchel, Moncada, Hendricks, Kimbrel, and Rodon.
Factoring in TA (9.5M), Gio (8M give or take), Eloy (6.5M), and Robert the Sox are now at $166M. Picking up Hernandez's option, and bringing back ReyLo and Engel puts you at around $178M. The Sox would essentially have to run it back with the same squad in 2022, but would go into 2023 with Keuchel, Abreu, Rodon, and Kimbrel's money off the books.
In a vacuum, I think the Rodon QO and the Kimbrel option would both be favorable for the Sox; however, selecting both would be a bold use of limited financial space in 2022.
All of that being said. if the Sox believe that Rodon will be healthy in 2022, then you have to extend the QO. You simply cant get that upside for 18M, while also keeping the 2023 budget flexible.