It does, it has a device called a FPGA, specifically a Actel A3P125 in VQG100 packaging if that gateway manufacturing cost/profit page is to be believed.
Here is the datasheet for it
http://datasheet.octopart.com/A3P125-VQG100-Microsemi-datasheet-27724211.pdf
It is a 125,000 gate FPGA without many extra features/additional memory*, fairly modest by today's standards really. That same datasheet lists a million gate chip and more expensive ones are considerably more powerful and it only gets worse from there (
http://www.digikey.fr/product-searc...ee=0&rohs=0&quantity=&ptm=0&fid=0&pageSize=25 )
*you can of course turn your FPGA's gates into memory but it is quite costly in terms of the number of gates needed compared to the storage you get.
What is an FPGA
A nice presentation from the recent C3 conference
Another presentation from an earlier C3, not quite what the gateway's one is up to but what others can do
Back on flash carts I am not sure what it could be turned to in this case. Most people use them more to avoid having to make custom chips aka custom asics, a very expensive activity though it has come down a lot for some older types of chip (some speculated that the sky3ds sort of did this by turning their FPGA design into one).