I doubt valve would make a L4D VR, certain infected like hunters would cause immense issues for normalfags and journalists and valve is focused on making VR as easy as possible to get into for retards which is also going to mean no verticallity/climbing and small in door maps so they can keep the requirements as low as possible.
Although maybe the game would be survivors only or have it so flatscreeners would play as the infected against VR players?