It'll increase in size dramatically. RAW will run about 10Meg, but it's the difference between 16bit and 8bit. The RAW, as I've been reading, is the equivalent of an unprocessed Negative that will never lose its original data or clarity, no matter how much you modify it.
From Canon USA.
JPEG, RAW (Canon .CR2)
(1) Large/Fine: Approx. 3.8MB (3,888 x 2,592)
(2) Large/Normal: Approx. 2.0MB (3,888 x 2,592)
(3) Medium/Fine: Approx. 2.3MB (2,816 x 1,880)
(4) Medium/Normal: Approx. 1.2MB (2,816 x 1,880)
(5) Small/Fine: Approx. 1.3MB (1,936 x 1,288)
(6) Small/Normal: Approx. 0.7MB (1,936 x 1,288)
(7) RAW: Approx. 9.8MB (3,888 x 2,592)