Please tell us what platforms are you going to support.
It would be great to make it working for S60 3rd Edition, for non-touchscreen devices too. Of course, such devices will have some features like orientation and accelerometer disabled.
I have no idea if the new Qt Web Runtime will be available on old S60 phones.
However, I think those phones already have some kind of support for an old version of Web runtime: "Symbian WebRuntime quick start":http://developer.symbian.org/wiki/index.php/Web_Runtime_(WRT)_Quick_Start
Basically, it will be used anywhere Qt is available.