Given the rate at which Chrome is revolutionizing browser related technologies, I even think Chrome might overtake Firefox in market share very shortly.
Chrome has attained in its first year the same average market growth of Firefox (roughly 4.5%) that it attained in 5 years with paid referral programs and advertisements everywhere. I wonder what growth Chrome will attain when it hits the rapid phase of its growth.
Also to consider is Microsoft is shipping Windows 7 in Europe with IE, Firefox, Chrome and another IIRC.
Additionally, Firefox grew its users base by 40% in the last year--adding nearly 100 million users.