More like Jump needs a constant flow of new manga in order to survive as a magazine. OP, HxH, MHA, BC, TPN won't be around forever, they will end no matter how recognized they are. Jump has always given anime adaptations to the majority of their successful series, at least since the 2000's and they'll continue to do the same. Most series seem to get anime adaptations announced at around 75-110 chapters in, and all the successful manga from the 2016-2017 period have enough chapters for their anime adaptations.
If anything, I think the magazine is flourishing, because of the fact that Act-Age, a manga from 2018, is the oldest thing without an adaptation. That means all the newer series are taking off well in the present day manga market.
Even if Bleach and Gintama are well known, it doesn't matter to present Jump, the magazine is always evolving and it needs new manga all the time in order to survive, this is how Jump has maintained its success.