The touchsceen interface is single touch, which allows mouse implementation as a bonus, which I among others tend to use.
Multi touch would obviously provide extra functionality but since there are 3" screens out there on early zynthian kits, multitouch is only really relevant on larger screens, and a LOT of discussion would need to ensue to define precisely what we as a community and the offical zynth might support.
IT has been discussed but the general conclusion it’s somewhere near the back of a very long list… 