It's not exactly an easy thing to do, write drivers.. especially high quality ones.. without a whole lot of vendor assistance.
If a driver does show up, it'll be because someone chooses to write one.. this may or may not happen.. everyone is free to do the work and send a patch to the mailing list.
A USB wireless card is far less than $100, it's closer to $30..
run(4) devices do support 802.11n, but OpenBSD's wireless stack doesn't support it yet (..regardless of the device).