ASUS's Best Buy exclusive RT-AC1900P Dual-band Wireless-AC1900 Gigabit Router is not a great leap forward from the RT-AC68U.
Edimax' Gemini RE11 AC1200 Dual-Band Home Wi-Fi Roaming Kit takes a different, and cheaper, approach to building a mesh wireless network.
Linksys' WRT3200ACM AC3200 MU-MIMO Gigabit Wi-Fi Router is another example of a router with technology waiting for devices to catch up with it.
Arris' SBX-AC1200P SURFboard Wireless Network Extender with RipCurrent is a nice little powerline-connected Wi-Fi extender, but trapped in a G.hn world.
Arris' SBR-AC1900P SURFboard Wi-Fi Router with RipCurrent G.hn Technology combines a conventional AC1900 class design with an underdog powerline networking technology.