To answer your question simply is No. Not many people want a 36" TV anymore unless it's going in the bedroom. Everybody wants bigger and better all the time. Also having a 4K panel in smaller sizes is kind of waste in my opinion. You wouldn't benefit from it as mush a a 55" and up. As for a 21:9 TV catching on or finding one, there is one already but it is not 4k it's 1080p. Unfortunately it hasn't really cached on. I guess it's good for watching black bar blue ray movies, as it would fit the whole screen but for TV cable it doesn't work , it only fits part of the screen unless you zoom it and you wouldn't have a clear good picture.
Vizio XVT 3D CINEMAWIDE® RAZOR LED® SMART TV
TV - Panasonic 55GT50Main Speakers - Klipsch Gallery G28'sCenter Channel- Klipsch RC-52Sub - Klipsch Sub 12Surrounds - Klipsch RS-52 II (new)Bluray/Game - HTPC/PS3Receiver - Onkyo RC-360HTPC - Intel Core i3, HDMI,Windows 7,XBMC,Bluray,3 TB,wireless WMC keyboardVideo processor - Darbee