Toby Fox and gang had a livestream this weekend, playing through the game. A bunch of new content was added, most of which we'll probably never get to see again, including a bunch of lore and a few new areas. They fought Snas on a true pacifist run and they said something about it being available online to play. So the fight is playable in a browser, along with one of the other fights, but that's it.
https://undertale.com/10/
