Do I really need to upgrade my Motorola MG7550?

Xfinity sent me a note telling me that my device is no longer up to snuff due to speed increases on my account or in my area (or both).  Seems to be officially rated for service up to 300Mbps, but I'm getting 350 down/12 up according to speedtest.  The Moto isn't particularly new, but seems to be holding up just fine??