That's what various advocates would have you believe. Mostly, what those are based on are a 1 or 2% slide over the last three years - you're supposed to assume that trend will last forever and extrapolate accordingly. The same sort of calculations that global warming wackos use to "predict" average daily temperatures of 240 degrees fifty years from now, IOW.
I'm referring to Windows's five percent drop in the web browser "user-agent" share from June 2004 to February 2005.