Global wireless sensor shipments total 45 million in 2011, with "strong growth expected for 2012 and beyond" ABI Research reports, as wireless pervades home automation, home entertainment and smart metering sectors.
ZigBee leads the market, particularly in the WW smart metering arena. The ZigBee/RF4CE will also grow within the residential space-- ABI forecasts combined home automation and home entertainment growth will total $300 per annum by 2017.
The move from IR to RF remote controls and a growing need for interoperability between "hub" and "node" devices remain 2 factors driving growth for standards-based low power connectivity.
Not that ZigBee has a monopoly over wireless sensors, mind. Bluetooth Smart should disrupt the low power connectivity space, while proprietary technologies should continue dominating "many markets" for at least the next 5 years. Low-power wifi could also be a major competitor in the long run.
With the ability to have almost unlimited node counts within a system, ZigBee/RF4CE faces a future with "a lot of room to grow" ABI concludes, despite competition from other technologies.