Respawn shortly thereafter deleted that message and offered up the response, "We don't, sorry. I saw 'Xbox controller.' We support 360, not One on PC." More than likely, this isn't an issue that's up to Respawn at all; like the rest of us, they're just waiting for Microsoft to release new drivers drivers that would untether the Xbox One controller from its current console exclusivity.
Reaching out to Microsoft for comment, a spokesperson said, "The Xbox One controller, although it looks similar in many ways, shares no underlying technology with the current Xbox 360 controller. We know PC compatibility is important to many Xbox One customers and expect PC drivers to be available in 2014."
We've also contacted Respawn regarding the statements, but it's likely that the PC version of Titanfall will eventually be able to to support Xbox One controllers. That that won't happen until Microsoft makes them available, but you might remember that hacker Chris Gallizzi claimed to have gotten the driver situation sorted out himself months ago.