I'd add C: one other person else will, but it's only an option through technicality because they are not at all good at it.My honest answer? "Hey, man, can you at least give it a try? Everything we do was new to us at first. I know that change is uncomfortable, that's part of human nature, but I'm really excited for this and I'd love you to join us."
If the person still doesn't want to? I strongly reconsider how much I want to be friends with that person, because FRIENDS are willing to try things with their other FRIENDS, to at least give new things a chance.
In my experience in a "D&D ONLYYYY!!!!!" group, what will happen is either (A) no one picks up the baton and there is no gaming until you, the forever DM, take up the baton again; or (B) someone half-asses some DM-ing and you remember why you didn't bother to be a player.
Cynical? You betcha.
After I converted my group to D&D-mostly-but-we-also-try-other-things, now when I am burned out an need a break, someone will run a mini-series of (not-D&D) and that works great.
That goes back to the perma GM who is stuck or they ultimately walks on a group of friends. The last group I walked from that person was one of two wall flowers who would gm if forced but the game became an excercize in main character+sidekicks with the main character being a fairly textbook dating the gm trope scenario with one's kid & the other's boyfriend depending on who picked it up. Last I heard from them it floundered a bit and I had no interest in going back to run 5e or play the role of a sidekick like robin.