Yes but those displays are stretched over a much wider field of view. When I sit on my couch and look at my TV it is covering maybe 30 degrees of my FOV. A VR headset typically would like to have 100+ degree FOV, which means a 4K VR display will have way less fidelity than a 4K TV.
This is the fundamental struggle with VR displays. Human eyes have very good visual fidelity and it would be real nice to match or exceed that with a VR headset. This presents many technical challenges.
Yes, it is around 3400ppi. This has been achievable for a bit in very small displays (these are 1.4in), although I believe there are difficulties with anything larger.