As @ken-martin said, vtk-m is the project where much of the GPU and many-core processing work is directed. I’m not saying this approach isn’t also a reasonable one, but in terms of community interest, note that vtk-m is the project where that interest is directed for a number of core VTK people. @RobertMaynard may have more to say about that.
What is the status of the GPU integration in ITK? That have some focused effort starting around 2010, but I’m not sure if anyone is still pushing on that.