No one is out there that is going to guarantee that by making a trade they will get us to the playoffs. So why take the risk of trading a potential late lottery-odd pick for a player that at best makes us marginally better. Certainly there are trades that could happen on lower level players, but they won't move the needle on us getting to the playoffs. Similarly, any trade of DDR or LMA is likely to yield less talent in return and given DDR free agent status and LMA's age, neither are likely to land a quality first round pick that would make trading them worth it. No reason to sell our best players to get junk assets.
Best course is to just try and make the playoffs with what we have with the possibility that there is a trade of one of the lower level players. Sure, if a once-in-a million opportunity comes up, then trade one of our two best players. But that is just very unlikely. Trading for Gordon or Winslow, in my opinion, is a downgrade if we give up DDR or LMA. Better to just see what happens this year. If DDR walks, then the Spurs have a bunch of cap space or maybe they do a sign and trade in the summer, but no reason to deal him now unless some unexpected miracle deal comes along, which is highly unlikely.