There are multiple career paths for developers. Project Management, functional management, software/system architecture, and senior development roles.
Project Management and functional management, like Development Manager, Team Lead, and CTO, are the management positions, with project management being more about managing project success and functional management being more in-line with team success, both tactically or strategically.
I've heard of developers heading into system architect roles, which is really just a senior level technical position that doesn't involve people management as much as it does determining the overall architecture of large systems.
Senior development roles are more like the position that you're in. Management likes people like you because you can use your experience to solve complex problems. While technologies do change a lot and you may feel like your coding skills aren't what they were in the past, the concepts behind problem solving are fairly static.
I've seen senior developer roles where the senior engineer was more independent, like a sole developer on a one-person team. A position such as this could be a great perk for an experienced developer who doesn't want to move into a management-type position, yet he/she still doesn't want to have the same type of hands-on management that a junior developer might face.
You might consider talking to your managers and finding out what your options are; they don't even have to be formal. If you're indeed a valuable person in the organization, they'll find a position for you that both utilizes your skills while also keeping you engaged.
Finally, a degree can help you break through this ceiling that keeps you from progressing. Consider discussing with your employer to see if they'd be interested in helping you obtain your PMI. It's not clear which path you're most interested in, but expressing your interest either way may at least let you know where you stand.