I think the role of the successful product manager hasn’t changed that much over the years. It is and has always been a glue role to help fill in the cracks on teams. Probably the biggest change over the past 15 years is now we have so much direct data flowing from our users, product managers need to be much more adept and fluent in handling data and communicating learnings from data. When I was first shipping client software on a yearly cycle in my first job at RealNetworks, product managers had to get market data and user interviews as much as they could. Now we have a realtime data stream of what many users are doing and can learn from there and adapt quickly.
I don’t think the role of design has changed anything here. The best product managers should always have deferred to and supported their design team to make something amazing. Maybe as an industry there is a better recognition of that though?