Just How Many AV Sigs Will the World Tolerate?

Dark Reading - Application and Perimeter Security - Malware Volume to Double by 2008 - Security: "At the current pace -- 2006 should see more than 60,000 new threats, up from the 56,000 during 2005 -- the 400,000 barrier should be broken in under two years,"

Is anybody else asking this question: does the current anti-virus model make sense in the long-term? Maybe Sanas and others will rule the world with their signature-less AV? Or will they?