There's no telling what will happen to growth in the 2,831 days between 7/1/12 and 4/1/20, but at the current average daily rate the 5 counties in NE FL are growing in the 822 days between 4/1/10 and 7/1/12, the metro will not even reach 1.5 million people in 2020's Census, it will come just shy.
By contrast, SF County would reach 901K people (Duval will stay larger), which would put it at 19,224 ppsm including park space (est 21,330 without).
Fulton County in Atlanta will grow 30% from 920K to over 1.2 million, and overall the 5 core counties of Atlanta will grow over 19% from 3.365M to 4.015M, which is an even spread of ~2,350 ppsm (1,713 square miles vs 3,698 square miles in the 5 county Jacksonville MSA)
Jax MSA (2010 Census, 2012 est, growth, nominal daily growth rate, 2020 Census est, decadal growth)
Duval 864,263 879,602 1.775% 0.002% 934,544 8.1%
St. Johns 190,039 202,188 6.393% 0.008% 250,290 31.7%
Clayton 190,865 194,345 1.823% 0.002% 206,823 8.4%
Nassau 73,314 74,629 1.794% 0.002% 79,341 8.2%
Baker 27,115 27,086 -0.107% 0.000% 26,986 -0.5%
Subtotal 1,345,596 1,377,850 2.397% 0.003% 1,497,984 11.3%