I am considering buying a 4D Systems I2C LCD for the BBB, e.g. a 7" touchscreen, which uses the I2C2 bus.
The question is, will I be able to use other peripherals on I2C2, on a home made cape, alongside the LCD ?
Ask 4D, or the 4D forum.
However, it looks to me that the I2C bus is used only for an on-board EEProm interface. Probably to store/read setup and user data. I would guess that there's plenty of bandwidth left over on the bus for you to use.
Do be aware that this board has the pull-ups already installed for this bus, so be careful about adding more pull-ups elsewhere. See the "ID EEPROM" section of the schematic in the datasheet, Page 8.
What about this one? It's from Newhaven Display and it's more inexpensive than the one you're looking at. http://www.mouser.com/new/newhavendisplay/newhaven-beaglebone-cape/