Worst case scenario - you get to #30 and the best board/scheme fits are gone and you can't find a partner to trade down. Now you end up reaching.
Best case - Queen or Murray are there along with an OT option like Jones and a top 4 receiver drops that far. You get your pick. Not gonna happen but hey, I can dream.
To me a trade down isn't really best or worst case scenario by itself. It depends on your board. Let's say the two LBs are gone as are the Rd1 OTs and the next best available WR on the Packers board when they get to #30 is #45 on their board. They don't really like their options at other positions except there is a safety they really like who grades out as good value at #30. What they should do is draft the safety OR if they can make a move from #30 to say #37 and get the WR then do that. Stay true to your board. Especially at WR, where the difference between these guys isn't real huge after the top 4, IMO. Why draft a #45 guy if you're picking at #30 when you can probably get a good a WR at #62 or even #94.
I don't think bailing out into the later part of Rd 2 makes sense unless you get an offer than just blows your mind, but a move down of 5-10 spots makes sense if your draft board says it does. Since we don't know how the Packers view the players, many/most (including me) will probably complain if they take a guy we feel is a reach, or if they trade down when there's a guy there that we think is great value at #30.