How often does Porsche come out with new variances on the 911? The 996 has been around for 5 years. Does this mean that the 998 will be a reality by 2010?

 

No - earlier

 

MY2008 introduced in 2007, expected to be released with the 4 door sedan (E2 for now)

 

Yes, that's what I heard too: 2008
It is said it will be a "major" evolution forward.

 

I just read this somewhere, Automobile I think. They date the 996 at 8 years, I'm assuming they consider '97 (as a '98) - '05. This is they expect a facelift on the 997 in two years and the 998 sometime close to 2010 if I remember the article correctly.