> is there a physic engine integrated?
Not yet. We had Chipmunk2D compiled in for awhile, but we haven't hooked it into Ruby yet.
> are the mobile targets going to be included or is it going to be a separate package?
We're trying to figure out how to package them appropriately, but at the moment we don't plan to sell this as a separate product.
> what about services? like ads, gamecenter, steam, etc?
We aren't this far yet (and I will probably resist adding advertisements).
> Is there a plugin system in the plan to integrate those systems?
One of my great frustrations, as a Linux user, is watching cool Unity games get locked into Windows because they used a native plugin that blocked them from other platforms. I'm not saying we won't add something like this, but it makes me nervous.