11a isn't the next big thing. 11g is essentially intended to be a replacement for both a and b. It runs at 54Mbps but is backward compatible with 11b. 11a has been a standard for some time but never became as popular as 11b, because it costs more and isn't backward compatible. 11g is still in draft form, and yet is being jumped on by manufacturers.
20 to 30Mbps throughput is far faster than the 4 to 6Mbps of 11b, and far faster than the 10Mbps wired LANs that some places still use. Sure it's not as fast as Fast Ethernet, but it's not yet designed to be a complete replacement; you give up some speed to gain the flexibility of a wireless setup. If speed is that important, you find a way to get the wires run.