The change will use visa data from the fiscal year ending last October. I'm not sure but I believe eligibility is re-evaluated by mid-year, so this is why I *guessed* that there might be a change by late 2008.

http://www.ft.com/cms/s/0/1169f782-4...nclick_check=1
New eligibility rules included in the bill will allow visitors from 12 more countries – including South Korea, Taiwan, Brazil, Argentina, Greece and the Czech Republic – to enter the US without a visa.

http://online.wsj.com/article/SB1185...googlenews_wsj
The program allows nationals of designated countries to enter the U.S. for up to 90 days without applying for a visa before leaving home. Twenty-seven countries currently participate, including most of Western Europe, Australia and Japan. Now citizens of 12 more will be able to apply immediately, and it will be easier for other countries to join in the future.... Newly eligible countries are Argentina, Brazil, Cyprus, the Czech Republic, Estonia, Greece, Israel, Malta, Slovakia, South Korea, Taiwan and Uruguay.

http://thomas.loc.gov/cgi-bin/query/z?c110:H.R.1.ENR: