Most of us will end up paying since we are captive users. The problem I see is that newcomers won't see the appeal of their services and therefore fewer and fewer will use strava. As soon as the leaderboards don't really show your overall performance among people going through that segment (as it has been up to now), they become obsolete.
Strava is doing what Whatsapp tried to do... with Whatsapp backing off. Strava is charging for what's been free till now. And their problem is that for the last few years they have neglected the core of the network: leaderboards and rankings. Why would someone pay to see a leaderboard topped by guys riding in a professional race, or disregarding wind effect (as Garmin Connect does) or comparing team time trials to solo efforts? I live in an area visited every year by La Vuelta... and I have lost some modest uphill KOMs at 22-26 mph to professional guys riding behind a car at 38 mph (seen with my own eyes).