Those who study Electronics will know what is call a shelve life. All electronics componments has a shelve life as it need power to refresh its internal. The clear one is component like capacitors, battery, gas discharge devices etc. How long the shelve life is depend on type and storage condition.
JULY/2009 batch is very new! but possible.
See this :
http://www.reghardware.co.uk/2009/03/25/pioneer_plasma/
This is on business week:
http://www.businessweek.com/globalbiz/content/feb2009/gb20090212_424440.htm
http://newteevee.com/2009/02/21/pioneers-kuro-killing-a-tipping-point-in-the-plasma-era/
Last portion: A little history of Pioneer Plasma TV history
"Pioneer’s decision to end its plasma production was more complicated. It bought out NEC’s plasma business in 2004, used it as an OEM for its glass, but was recently forced to shutter the unit. Now, the only plasma manufacturers left standing are Panasonic, LG, and Samsung, all of which make their own components."
Many may have forgotten this company call NEC, they are one of the pioneer of plasma display panel.