Asking on behalf of spouse
PMMs are valuable if an org understands them but the role seems to be absorbed into PM and marcomm/digital marketing departments at many companies, so from that standpoint digital marketing may offer more growth due to a larger department at most companies and the fact that all companies have digital marketing roles whereas not all have PMM roles. PMM can at least pivot more easily into PM than a digital marketer though.
Why would you say that? (Although I like your prediction. I want to move back into PM)
In companies where PMM doesn’t exist, PM usually covers most of their role and a good PM should understand the customer the same way a good PMM would. There is a lot of skill set overlap.
I’m a Product Marketer and I must say that it is the least understood, least cared about role in marketing. The CMO only cares about those functions that he can measure, and show to his boss, the CEO, and his major stakeholder the VP Sales. Digital Marketing (a broad term encompassing demand generation, corporate marketing, online marketing) always has numbers attached to it. Product Marketing does not. Product Marketing I believe will die out