First sentence is true. Second sentence is true but not to the point that it eats into Fitz. Thrid sentence is half true. Arians absolutely WILL affect the targets to Fitz, as will having a real QB, as will having a better o-line, as will having other pieces in place.
Even in the consensus picks of experts (pools of 15-30 fantasy "experts" predicting stats and then grouping them in averages), the typical predicted number of catches for Fitz this year is 100+. That is a LOT of targets. I think it is clear that the experts reading the tea leaves are giving Arians' impact into this major consideration. And why not? 90% of the world thought Wayne was dead before last year and he crushed it all year (2 games with less than 10 fantasy points? Really? That IS consistency.) So, the idea of what he will do with a talent like Fitz and a QB like Palmer is certainly enticing to say the least.