A modern Qt browser would require porting QtWebEngine, which I think is about as much work as keeping our WeKit port up to date.
Not that this should prevent anyone from doing either.
A few weeks ago I have resumed work on updating WebKit, and I am currently tracking the regressions I introduced while doing so. Once I fix them, there will be a new WebKit package, hopefully with less bugs.
As for GPU offloading, most web engines do that, including WebKit. We just disable it at build time.