Some good points raised here, particularly around bandwidth, cost, and security concerns.
Here's one more point - wireless networks can be seriously degraded by EM radiation. A datacenter is one of the most challenging RF/EM environments that one could possibly imagine. I would be very surprised if you could get consistently reliable connections, without frame drops. Think of all the EM interference!
Finally, there is constantly a drive within the datacenter for [consistent] low latency. Wireless technologies have higher latency than wired equivalents. Is this technology going to actually be useable?