There is about 3.. Broadcom, Qualcomm and MediaTek. Together they control I believe 100% of wifi chips used in routers and APs. Often it's sold as a package / system on chip so it's also the main cpu.
On the client side there is a little bit more competition but not much.
I am also not sure of their exact market shares but I would suspect one or two are probably steering the majority of the "standards". I'd suspect Broadcom and Qualcomm to have the most influence.
But I agree, Broadcom and Qualcomm are the heavy hitters.