What innovations can we look forward to, and what problems might we face?
Standards that allow coexistence between current and upcoming protocols are in development.
This IEEE group (802.11h) is developing transmission power control (TPC) and dynamic frequency selection (DFS) protocols. These protocols will use the band more efficiently and be required for European deployment.
The standard is expected to be available soon. Atheros Communications, Inc. is already starting to ship 802.11a chipsets with these features.
The 802.15 IEEE task group is developing a set of "Coexistence Mechanisms" that will facilitate the coexistence of WLAN and WPAN devices with methods such as "Data Rate Scaling."
The subgroup of "Working Group on Broadband Wireless Access Standards" for Metropolitan Area Networks (MANs) is called "Coexistence of Fixed Broadband Wireless Access Systems." This group is researching what it takes to deploy a MAN and to solve interference issues.
New sources of interference and organized opposition to wireless community networks may make deployment more difficult.
Some companies have experimented with excited sodium lamps that use RF energy from 2.4 to 2.4835GHz. Such lamps have a broader and more contiguous spectrum than mercury vapor. They are also four times more efficient.
ISM band users are concerned that this type of lamp could add considerable noise to the 2.4GHz band. Short- and long-range 802.11b could be crippled.
The ARRL is very active in commenting on proposed rules that would give more spectrum to unlicensed users. They are particularly concerned about spectrum that is currently used by amateurs. Some insight can be gained at the ARRL's page on Part 15 devices at http://www.arrl.org/tis/info/part15.html.
The NTIA/IRAC is concerned about this spectrum, because they also use it. However, the exact use may be secret; it isn't really defined anymore than "radionavigation" (read: RADAR). They are also very concerned about future Ultra Wide Band developments and have sent out a number of "hand slaps" to the FCC for their recent rulemaking on UWB. It is likely that they see the ISM and U-NII bands for what they are and have given up on it and moved any low EIRP communications from it.
Some people are also concerned that 3G license holders may be actively working against 802.11 use, which can be seen as very cheap competition to the very expensive 3G spectrum development and deployment. We haven't seen anything definitive, but keep an eye on this possible conflict.