Overall I think it would be neat to see a "hackable" (2D) video controller emerge too. There are quite a lot of "small systems" that could use with an easy way to get decent video out (practically speaking HDMI, or maybe DP).
A display controller that can drive HDMI and a 2D graphics accelerator are different things. They just both work from the same framebuffer in a SoC's memory.
A special chip isn't really needed for this, an FPGA can do all of the above (with the correct bitstream)
Fpga, discrete asic, or on-die on soc, that's just implementation detail. Of course I'd expect the first iterations to be fpga based, that's almost unavoidable these days.