I wouldn't say they took an immediate step backwards though. They did what was best for this season, the real impact of this trade will come next year when they have no first round pick.
I'm not sure thats true though.
Most WRs, even high ones, aren't impact players their rookie years. Mike Williams was probably the best rookie last year, at 65r for 954 yds and 10 tds, and hes kind of a case where Freeman is pretty good, and somebody had to catch the ball.
Here's the list of rookie WRs to break 1000yds:
John Jefferson SD Charger 1978
Joey Galloway SEA Seahawks 1995 1st
Terry Glenn NE Patriots 1996 1st
Randy Moss MIN Vikings 1998 1st
Anquan Boldin ARZ Cardinals 2003 2nd
Michael Clayton TB Buccaneirs 2004 1st
Marques Colston NO Saints 2006 7th
Most of these guys were high first round picks, but we're still talking about essentially 4 guys (Clayton, Moss, Glenn, Galloway) in the modern NFL expected to be game changers, and actually being that their rookie year. And Clayton is probably still considered a bust.
The most likely scenario is Jones has about 500 yards receiving, and 5 or 6 TDs. Is that enough of an impact to offset the 2nd and 4th they gave up this year? Maybe, probably not. Is it enough to offset the aditional 1st and 4th they gave up next year? Definitely not.