What is known of the capacities of the MINDSTORMS EV3 when it comes to interconnection with a network (WiFi, bluetooth)
The Mindstorms EV3 brick uses Bluetooth 2.1EDR. What protocol they use on top of that is still unknown, but will probably be released publicly by LEGO at some point. It's likely some compatibility with the NXT is possible (that is, an EV3 and a NXT bricks should be able to communicate together), but this is pure speculation and I doubt they just reuse the exact same protocol without at least expanding it.

For USB, apparently the regular USB port is 2.0, but there's also a host USB port which, according to the previous link, is only 1.1 (which seems strange to me, and the official PDF product sheet for the EV3 brick specifically mentions "USB 2.0 host enabling brick daisy chaining, wifi communication, and USB memory sticks") and can be used to daisy-chain up to 4 devices. The very fact they state a limitation hints that their software itself has this limitation, as I don't see any hardware reason to do so. This means that with an alternate firmware, you can probably do more.

WiFi is only possible using a WiFi dongle connected to the USB port, which seems to be allowed. If the host port is really 1.1, that may limit the speed to 12MBit/s. You can find  its PDF product sheet here which says:

The EV3 Wi-Fi Dongle fits with the LEGO® MINDSTORMS® EV3 platform and uses wireless communication. It plugs into the USB host port of the EV3 Intelligent Brick and provides wireless communication with a computer. A wireless access point is required between the LEGO EV3 Intelligent Brick and any Wi-Fi -enabled computer as well as your Apple or Android device. All you need to do is set up the connection inside the software and you’re ready to go!

Also, considering the OS is linux-based (on an ARM9 processor), and considering LEGO's history of letting people hack Mindstorms in any way they can think of... there'll probably a lot of other possibilities (USB Ethernet, for example).

APIs and/or libraries aren't available yet, and probably won't be until the kit is released, but it seems there'll be at least an official iPhone &amp; Android app to control all robots you can make with the kit.