I think that this year the dominance of the top three teams (GS, SA, and CLE) will probably make some of the 2nd-tier "contenders" a little gunshy. Why lose assets in a futile attempt to overtake on of those teams? They're so good that it's not going to be as simple as just adding a solid role player. Neither do some of these teams have the assets required to get a real star.
I guess conversely you could say that the top-heavy nature of the league this year will trigger a sell-off from some of the teams that have used up their bullets and now have to start admitting to themselves a title isn't possible anymore. A team like Memphis comes to mind. I know they love Gasol and would probably keep him if told them he wanted to stay, but if they dealt him now they could really set up their team's rebuild. Conley would also fetch something nice, but he's still young enough that maybe Memphis re-signs him and keeps him around like the Blazers are doing with Lillard.
The Rockets also look like sellers when it comes to Dwight Howard. This year has proven there's something wrong with this core and since they can't give up on Harden, Dwight is expendable. Chicago looks like they want to take a slight step-back and build with a core that is closer in age to Jimmie Butler, and that means saying goodbye to 30+ year-olds Gasol, Gibson, and Noah.