Ok cool. And you're right, the UART is being connected to the FTDI IC. Another option would be to add a UART-to-SPI IC and have it communicate over SPI, however I don't know if there are any advantages to that. Not to mention the addition of more components (UART-to-SPI IC, crystal).
My idea of using a ready made RN module, like the RN-XV WiFly Modules that SFE sells, is because it makes everything modular. If something happens with the unit, I can simply pull it out and replace it for another one, as opposed to having to junk our entire board. And it also allows me to add a W5100 to the board and give the end user the option of either wired or wireless communication (but that's thinking out loud.)