1) Good idea - pascal is set to be a nice upgrade over the current gen.
2) Even with pascal, running a 4K monitor for gaming will still require a powerful SLI set-up to achieve good performance. A nice 1440p monitor with a high refresh rate would be much better for a single GPU.
3) Because movies are not being rendered in real time, and are shot at much higher resolutions then scaled down with heavy editing and post-processing.