From what I've seen so far, it looks like it should be able to handle at least 20 different devices sharing the same virtual tabletop. I haven't been able to test this since I don't have that many devices, but it should be able to easily handle your typical group with room to spare.
Yes, there will be an offline mode, for using the app much like you can now. You won't be able to connect to other mobile devices running the app, but you can pass it around the table and display the virtual tabletop on an external screen such as a big TV, as long as the device you're running it on is capable of that.
The Kickstarter version will be a free upgrade and you'll be able to use all the new features in offline mode. With a subscription you get multiplayer networking for sharing the tabletop with other people.
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