I would argue wireless is now more the norm than not. Everywhere you go, there is WiFi, and it's getting to the point where there is almost no difference in quality between wired and wireless. Not quite yet, but almost. Game companies should keep up with the times. I already have a web of cords for all my game consoles and my TV, plus the modem and the router cords, etc. I don't want to add one more cord.
I'll grant you that at this point in time, wired is a little more reliable, and for a fighting game where split second decisions are required, yes, for competitive play wired is probably preferable. For casual players like myself though, WiFi or not it makes no difference. I've had plenty of good connections matches in MKX over the last two plus years.