LEGO has been teasing this on twitter, and some leaks came out a few days ago, but yesterday they announced LEGO Dimensions (see the official announcement on Brickset and the new website on lego.com.
I haven't read everything, and I'm not a gamer, but it looks like this is like Skylanders or that Disney Infinity game, where you get a little model - e.g. this

and put it on a electronic thingy, e.g. [url=https://www.flickr.com/photos/tormentalous/16880895227/in/set-72157649529408293]this

and then that model becomes part of the game world. You can buy additional pieces that bring different characters or vehicles into the game world.
Some points and questions:
-I do not know if those models are solid plastic, glued together LEGO, or actual LEGO pieces you can take apart.
-Interesting mix of themes - LEGO movie, Batman/other DC heroes, Lord of the Rings, Back to the Future, Ninjago, and ... Wizard of Oz?????? I'll start another thread in General LEGO on that question
-From the released screencaps I assume these figs all mix and match in various worlds. E.g. this pic shows Marty McFly and Gollum in Oz.

-Does this mean that the Collectible Minifig game is no more? It seems that this is essentially a souped-up version of that. Will these compete with each other? Or will one or the other die? If the CMF game dies, will CMFs come down in price? It seemed that the increase in price was part of the monetization of that game.
-What, if any, other themes will come into this game? I saw a comment that we probably won't get either Marvel or Disney themes in this because this directly competes with Disney Infinity. Surely all non-licensed themes are potentials, so we could get pirates or general castle guys.
Anyway, what are your thoughts? Are you excited? Disappointed? Feeling meh? Looks like it releases on September 29.
Bruce