I still think Duncan is more likely to return than not, but we'll see what kind of shape his knee is in after the season and whether he thinks it can hold up for another season.
Either way, they won't be able to afford Horford, Noah or Mozgov and don't have the (realistic, since they're not touching the core) assets for Lopez. Noel is also not affordable and they'd more than likely match any offer he might receive anyway.
Milutinov, even if brought over, is obviously not an option to start next season, Jean-Charles isn't a center and neither is West. It's one thing to play it for two stints a game, mostly against backups, but it's another to do it full time against starters.
Varejao, Hibbert, Aldrich and (Miles) Plumlee, are more realistic targets. In other words, 20 mpg stop gaps, with Aldridge and Marjanovic soaking up the remaining minutes.