An SA2000 helmet will be good until January 1,2011. So yes, you are ok with most sanctioning bodies until that date.
Hopefully Snell will release the SA2010 standard in the next few months to allow the manufacturers time to design/build test units to submit for approval to Snell for testing. Then once they have approval they can begin making SA2010 helmets. In the past (except for SA2000 which was a drastic departure from SA95 causing many manufacturers to have to completely redesign and one, Shoei to bail from SA helmets altogether) the new helmets start to become available in mid to late calendar year.

cheers
dave parker