I think the pressure that has the ability to change Sony's mentality is more likely to come from the developer side of things
No, I'm not missing your point. Forget lawbreakers for a moment. Think of less popular online games. Is this helping?
The general public cares for the big games and those that generate enough noise.
Those are the main drivers in console and software sales in which Sony clearly leads and even increases all the time.
The masses care about CoD,GTA,Fifa and stuff and there everyone thanks to advertising knows you "have" to go with the PS4.
Even recently with the currently biggest game,a free2play game like Fortnite it was made clear a guy like Drake plays on PS4 with his buddy Ninja who is on PC.
Perfect advertisement.
The masses see Drake is on PS4 and he crossplays with PC and that is enough.
Would it help smaller games with next to no advertising and no media presence on for example twitch&youtube to have a somewhat bigger community?Sure obviously
But they don't matter - They aren't important enough to actually affect the mindset of the general public and they won't hurt Sony or whoever might be currently excluding someone from the party.
And reading something like "Sony will feel it once developers don't release their games on the PS4"
Sure sure - EA,Activision etc won't release Fifa,CoD&co anymore on a soon 100 Million Installbase platform anymore
Not even Epic with Fortnite will change anything - They can silently grumble around but you don't exclude the PS4 aka the Console Industry Leader anymore if you have a game that is big and good enough to make it into the mainstream market.
The only pressure Sony might feel is if Microsoft manages to start selling anywhere near close as many consoles as Sony currently does + increase their Worldwide presence which they clearly don't.
As long as this isn't the case not a single one of the big publishers that could start a change of heart will go against Sony cause they are the definitive choice to bet on.
What i can see is Sony changing it on their own and advertising it big at a event on the stage to make it their good news.