I confidently predict the 50D to be announced in August 2009. Anyone care to speculate on the specs?
Your maths is incorrect:
20D: September 2004 (when I bought mine)
30D: PMA 2006 (Feb/Mar) (when I yawned and struggled to keep my eyes open)
40D: September 2007
Gap of 18 months.
You should "confidently" predict the 50D for PMA 2009.