Looking for elliptical display or modular display to approximate ellipse
The simplest and lowest cost way to get touch displays this size is to use rear projection. With curved optics and mirrors the projector depth can be quite small (1 -2 feet). There are many examples such as from Draper: http://www.draperinc.com/projectionscreens/rearscreens.aspx
Microsoft's Perceptive Pixel also make rear projection touch screens this size.

With the availability of 4k projectors now, you could implement a quite high resolution large touch systems.  

You could also build a large display of multiple edgeless touch enabled LCD monitors, but you can never quite do it without some gaps in the display. It also needs much more graphic compute power as the number of displays rises.