The question is hypothetical and presumes
1) a 5DIV would improve generically on the 5DIII but with a significant MP boost (at least 32MP compared to the existing 22MP for the 5DIII)
2) the price range of such a camera would follow the pattern of the 5D-family (around 3.500$ at launch)
1) a 5DIV would improve generically on the 5DIII but with a significant MP boost (at least 32MP compared to the existing 22MP for the 5DIII)
2) the price range of such a camera would follow the pattern of the 5D-family (around 3.500$ at launch)