There is my current "home network' setup. We built a house about a year ago and this is where I stand. Upgrades from the picture are just AT&T fiber, 300up/300 down.
The nighthawk does a good job, a bit crappy upstairs in the attic (but I'm not there often, just a PITA when I'm trying to aim my antenna with a smartphone cutting in and out o f my HDHOMERUN app) and outdoors (cutting in and out 100 times while I work on the lawn).
So, reasons to upgrade would be
1) Range increases. All my important devices are Cat6 (server/gaming PC near router) or Cat5 (in the walls to HTPCs). Wifi devices do mostly well, but I would like a bit more range.
2) More wifi deviecs. I am nearing 15 DHCP reservations and I'm 90% convinced I get drops from so many wifi devies despite clearing everything and starting over.
This has been a great router. I improperly made a cat6 cable and ruined one of the in-ports...cut open a switch, stole a port, desoldered the R7000, and threw in the stolen port. My blood, sweat, and tears are in this thing. Is there any real reason to upgrade it even though its 3-4 years old? I don't think I'm interested in going the unify firewall/access point route...a lot of work compared to my setup that is done and 95% acceptable.