How do you motivate your product marketing direct reports with upward movement when there may not be opportunities for people management.

1. Give them interesting and stretching projects: from writing content to pricing and competitive intelligence.

2. Facilitate and incentivize cross-functional work: let them own and drive projects with other teams, e.g. customer sucess, bizops, etc – so that they learn a lot.

3. If you work for a high-growth company, the situation might change in a few quarters and the upward opportunities might appear – so people on your team should be ready.

Improve their skills. Prepare them to replace you (so you can get promoted). Or prepare them for their next opportunity. Help them build their resume. Not only is it the right thing to do, it builds loyalty.

Product marketing doesn't get people management opportunities as fast as other functions, so consider supporting a move into another role. Many sales and marketing jobs will be appropriate for an experienced PMM, and will include people management. You'll struggle to retain the people who really want to try becoming managers if product marketing is the extent of their opportunity in your company.

Keep them motivated, working on interesting things, help them continue their growth even if that growth means they're leaving the company. And the harder part in some ways... tell them your own aspiratations for growth and the potential for you to move up (and/or on) yourself. 

Think about it the other way. PMM is one of the most cross-functional roles in a company. You are essentially quarterbacking the entire go-to-market efforts. The leadership qualities required to motivate people who don't report to you is arguably more challenging than direct people management. While people management doesn't come easy in this function, there are plenty of opportunities to hone leadership skills.

Honestly, pay them more. You can also look at getting them MBA interns for the summer, etc. Also, depending on how big your marketing team is, you can give them expanded scope outside of PMM, if that interests them. e.g. have them manage a couple copywriters who are contractors.