[mindcrime]

Do developers without a degree have a ceiling in terms of career advancement?

No, since you can always start your own company and make yourself CEO.

Assuming you legitimately do have the skills, temperament, patience, $WHATEVER, you can literally go as high as you want. That is not, of course, to suggest that it is easy. I know, I went this route myself, and I can definitely attest that it isn't easy.

Also, have developers without a degree been able to transition into technical, product, or business leadership roles?

I think some guy named Bill Gates did OK for himself. And some dude named Zuckerberg...