Bethesda have spoke out on many things regarding The Elder Scrolls Online. A bunch of topics were discussed but news of cross platform play and the struggles it brings will be a slight disappointment for many. Whilst discussing the challenges of working on both new consoles, Bethesda vice president Pete Hines said, "They don't all play with each other. PC and Mac play together, but Xbox One is its own thing and PS4 is its own thing. The whole cross-platform thing is just a nightmare."
He did say however that overall the new consoles were easier to develop for individually. "I'm not trying to insult Sony or Microsoft, but they're high-end PCs, the way they're architectured. Though they're still in development, they're not done, they're much easier to develop for." He also commented on the Xbox One specifically saying "Are we looking forward to developing on Xbox One?. Yes. It's a nice robust machine that allows to do lots of cool stuff and put more cool things in the game."
Whilst the news of no cross platform play is disappointing, it isn't really all that surprising. With the games having to run on separate servers it would be incredibly hard to pull off with the current way the consoles work. Hopefully without this feature the game will still be a lot of fun.