In 2005 RFID spending was $504 million, a 39% increase over 2004, according to Gartner (registration required). Their estimate for 2006 is $751 million. Garner's study reports that RFID will not replace bar coding (which is cheaper), but will be used in applications that bar coding can't support.

"For the most part, bar codes are better at collecting data in highly
structured and engineered processes, such as warehouses, and this will
likely continue for the next five to seven years," Mr. Woods said.
"However, RFID tags will be used for data collection of mobile assets
and in largely chaotic or unstructured business processes, ranging from
retail environments to hospitals, enabling these environments that lack
sophisticated process engineering or controls to be systematically

They even have something to say about how RFID adoption is evolving in hospitals:

"In many cases, RFID will be used in areas where the process is not
controlled by an incumbent business application," Mr. Woods said.
"Contrary to the notion that companies will need to "integrate" RFID
data into established transactional applications, companies will likely
need to develop new business applications if they want to put RFID at
the centre of a process. In this, the opportunity for real process
innovation exists."

This jibes with my position that RFID is not a product but an enabling technology for new applications, like infant security, hospital wide patient flow, and departmental throughput applications (especially in the ED and operating rooms).

Gartner has published a series of reports that provide detailed analysis on the future of the RFID. The 78-page report 'RFID Enables Sensory Network Strategies to Transform Industries'
examines the factors affecting RFID adoption, as well as the impact
RFID has on vertical industries. Gartner has also released its
inaugural RFID market size, share and forecast report entitled 'Market Share and Forecast: Radio Frequency Identification, Worldwide, 2004-2010'. Both reports can be obtained from Gartner.