I can't in good conscience say Adams. Has to be Cobb until further notice.
Cobb has an established relationship with Rodgers, a fairly strong one that extends over the past few years. Adams didn't perform badly last year, but obviously he's got a large distance between himself and Cobb. This isn't to say Adams can't jump up to WR1 value and even have a better year than Cobb, weirder things have happened, but that's the long odds choice in that gambling situation.
As for trading for one of them with Hopkins, it's an interesting situation.
If you've got Hopkins, I would ask for Cobb, but not for Adams. We need to see the hypothetical large boost that Adams should get happen for real for Adam's value to reach Hopkins' high-WR2 level. It's very possible he'll do it, but any time a top guy goes down, who fills the void, if the void is filled at all, is tough to say exactly. They could increase Lacy's workload and get Cobb to 1,800 yards and leave Adams in the high hundreds instead of pushing him above 1,000 yards. Alternatively, Adams could explode to 1200+ yards and 10+ TDs. Still, in my opinion, a bird in the hand is worth two in the bush, so I prefer the high-WR2 lock compared to the guy with a likely WR3 floor and WR1 ceiling.
Meanwhile, if I had Cobb, and you offered Hopkins, I probably wouldn't take it. Cobb had 1200+ yards and 12 TDs WITH Nelson out there. Estimates, if they go anywhere, go up. Hopkins' yardage is similar, but there's a sizeable TD gap, which is why Cobb is a WR1, and Hopkins is a WR2. Still, if you have a little value to add in, it might be worth it, if the guy you're trading with is willing to sell low.
So, in short, if he gives you Adams and some value added, then trading away Hopkins is worthwhile. For Cobb, you'll need to add a little value.