OpenIGTLink is a communication protocol, used over plain TCP or UDP sockets. It does not address the issue of texture transfer from CPU to GPU. What we implemented in the above video is pasting arbitrarily oriented slices into a 3D volume using OpenCL.
Uploading texture to GPU on a separate thread should be no problem, but it may require some VTK changes. We did not have to implement it for any of our projects, so I don’t have first-hand experience with it.