I am about to buy a Canon 40D ($1149) and a Sigma 18-200mm OS ($429)

Should I wait for PMA to end to see if there is an update? Either Canon 50D or Nikon D90? Im sure there wont be a 50D but what are the chances of a D90 w/ weatherproofing and an increased fps rate? Possibly 12mp?

I really want to order this camera to get it as soon as possible but dont want to be impatient and end up regretting it.