If & only if Facebook sell access to capacity on the cable publically (They might just keep it for their internal use), and then if any of the providers that the gaming traffic uses start to use capacity on that cable.

However, fundamentally, even if fibre took the most direct route from your house, directly straight-line to the datacentre with the server in, and then straightline from there to your friends on the East Coast, the time taken to complete that journey and back is still going to be 150-200msec or so; so it won't be as snappy as if you all lived nearby, sadly.