The reality is that, unless it's a selling point for the game, we aren't gonna see very many devs actually making use of this. It's extra work and logistics that most bigger devs and pubs can just shrug off due to it not being like, a central default console feature. Great for cross-plat fighting games and MMOS, though I feel that even Elder Scrolls Online wouldn't have had Xbox / PS4 /PC cross play if it had been a thing back then.
...Plus there's still that bit about Xbone requiring Gold to even play F2P games and subscription MMOs. They should look into removing that first.
The Psyonix developers were posting on Reddit saying that it was fairly trivial and they had xbone/steam up fairly easily because of the tools MS gave them being decent. It's just a matter of Sony and Nintendo opening their networks. It's good news for any game that requires a solid player base online.
The catch really is that Microsoft's going to go hard in on making money off Sony and Nintendo over the next few years on top of their own platform as part of the company strategy like they did on Apple and Google (Hell they kicked Google in the dick in the Tablet market. Samsung's switching their flagship tablets to W10 and everyone else is following). They already own Minecraft and Havok Physics. Now they most likely want to start grafting money off other consoles online with the Azure virtual servers since to publishers, they would be cheaper than 24/7 physical dedicated servers as the charge is based on usage and Microsoft gets paid. Getting rid of cross play barriers would entice big publishers like EA and Ubi-Soft to start hosting games because "On Demand Virtual Dedicated Servers" are hella cheap compared to24/7 physical dedicated servers like EA uses for Battlefield because MS charges by usage. They only pay by the demand for the game. Say if Rainbow 6 Siege used them. Ubi would only be paying by the amount of players using the servers than a static cost for game servers.
If Sony and Nintendo agree to cross play on the PS4 and NX for a game hosted on MS servers, most likely Titanfall 2 for example. MS makes money. If they refuse because MS is hosting the servers. They look like dicks and idiots going against their own PR turning down good servers because the opposition is making money off of them. MS is taking an L this generation, but it's a profitable L if only for the fact they are setting up for future generations.
Oh and you are right. MS needs to drop gold for F2P and MMO's. That is still stupid but then they said they were going to talk more about the "Future" tomorrow at GDC and then at Build at the end of the month so god knows at this point.