Numbers can't explain everything. Of course you'd trade the house for a chance to get an MVP caliber player on paper, but trades aren't made on paper, they're made by people with a lot of different motivations.
First of all, if you are the GM with the top 3 pick you want to maximize the pick's value, right? But you also want to keep your job... so you aren't looking at it in an objective way. If you trade the pick you can get a lot of criticism not only if the player picked there is great, but also with the next 15 players or so... how do you feel about it? Also, you know you could pick the next Sam Bowie, Greg Oden or Darko, but you feel you can make it and draft the next Jordan, Durant or whoever. The risk perception of trading the top 3 pick is bigger, by a lot.
On the other side, if you're trading 4 unprotected picks (the other side will ask for them, as they see themselves risking a lot) you are focused on a player who will be available when you pick. It's one thing if you're getting #1 pick, and very different if it's #3, because as you go down on your draft board, you're less certain to make it right. Also, you need a lot of confidence and job security to take that gamble: you only have a chance to strike gold, if you screw it you're exposed. Danny seems like a guy who would take that risk, but if he traded 4 first rounders to pick the next Derrick Williams, Ben Gordon or you name it, he better make another KG trade.
I think it's very unlikely, and I'm fine with that. It's still very soon, but if you look at mock drafts, there are a lot of great prospects outside the lottery and even in the 2nd round. We shouldn't put our eggs on the 2014 Draft top 3 when everyone is buying into it. Sell high, buy on the cheap. Danny's drafting is quite good, and I'm sure he'd strike gold with that top 3 pick, but I'd still keep the 4 first rounders and get the flexibility and the chance to draft the next Rondo/Marc Gasol year in and year out.