Taking a look at how some somewhat recent teams did when adding a lot of talent, though not that I think anything is a great comparison to Brooklyn’s situation, but these are some teams that I think are somewhat comparable (already good teams with established alpha dogs adding good veterans and key role players, where talent coming in far exceeded talent going out, and you have championship expectations).
2012 Lakers finished with a full season equivalent of 51 wins, added Steve Nash, Dwight Howard, and Antawn Jameson and had 45 wins in 2013. -6 wins.
2009 Cavs won 66 games, added Antawn Jameson and Shaq and won 61 games in 2010. -5 wins.
2005 Heat won 59 games, added Antoine Walker, Gary Payton, James Posey, Jason Williams, Derek Anderson, and Jason Kapono, then won 52 games in 2006 (but won the championship). -7 wins.
2003 Lakers finished with 50 wins, added Karl Malone and Gary Payton, and had 56 wins in 2004. +6 wins.
2000 Portland Trailblazers finished with 59 wins, added Shawn Kemp, Dale Davis, and Rod Strickland, and finished with 50 wins. -9 wins.
2000 Heat won 52 games, added Anthony Mason, Brian Grant, Eddie Jones, AC Green, Cedric Ceballos, and won 50 games in 2001 (though that was the year Alonzo Mourning missed most of the season with kidney issues, but made it back for the last part of the season and the playoffs). -2 wins.
1996 Rockets won 48 games, added Charles Barkley, Kevin Willis, and Eddie Johnson, and won 57 games in 1997. +9 wins.
1996 Knicks won 47 games, added Larry Johnson, Allan Houston, Chris Childs, and Buck Williams, and won 57 games in 1997, +10 wins.
-6, -5, -7, +6, -9, -2, +9, +10. Most of the negatives are from teams that had won about 60 games or more. Really hard to improve from that point though. Biggest improvements are from teams that won only around 50 games (which is the Nets). Not a lot of championship success though from this sample. Though maybe I’m missing some teams, these are the ones I thought of (that were already good with an established alpha dog, adding a lot of talent).
Nets won 49 games last year, I see them winning somewhere in the 50-59 range. 55+ I’d say.