Possible but Improbable
As for seven-season records, the aforementioned 1990s Bulls and Showtime Lakers lead the way, winning 74.7% of the time. Every season in both stretches lasted for 82 games, meaning the threshold the facing the Warriors is 429 wins in seven years.
If Golden State won 57 games next season, they would have 430 regular season wins since the beginning of the 2013-14 campaign. Considering their record last year was 57-25 with a far more talented, albeit fragmented, roster, this will be a tough ask.
They would also break the record if they average 54 victories over the next two seasons. This figure is more realistic but, due to the depth of the Western Conference, it would still take an almighty effort.
At 74.2% the Spurs of 2011-2017 have the highest winning percentage over seven seasons since the turn of the century. To surpass this, the Warriors would need to win 54 games in 2019-20, or average 52 wins over the next two years, assuming they play 82 games on both occasions.