No. However, I'm not sure I'd look at the exception to rookies improving rather than looking at the majority of rookies who DO improve in their second seasons. But, if you'd like to assume that all rookies will get worse, then the front office has a LOT of work to do this offseason, like drafting three brand new WRs.
So, are the Packers assuming no improvement? If so, does that mean they need to go WR heavy in the draft again? Assuming the worst, less likely case, for rookies isn't really the best way to plan for team building, in my opinion.