Hey! I'm not a pessimist but have a mixed opinion about this statement.

• Obviously this condition is never going to achieve because all our wishes are interconnected in a way (in both the same and the opposite way). It's totally an imaginary condition.
  
• Let's just hope for a second, that such a condition appears even though after that, we will get new wishes. Our wishes are never-ending, even if Jack obtained his Jill, maybe life seems boring to him and he discovers a new Jill (I don't want that though, it will ruin our childhood). But yup wishes are never-ending.
  
• I think Schopenhauer is right in a way, that if such a condition appears then

there would be wars, massacres, and murders

but he conflict his own words, war, murders, and everything again ruins the equilibrium Schopenhauer trying to establish by fulfilling everyone's wish.


P.S.: There is a Bollywood film, named "God Tussi great ho" (God you are great), in that film the hero was angry with God because God is not fulfilling people wishes, so God gives him this opportunity to fulfill everyone's dream and then films goes on...(explaining things from different aspect). Film is not great though, but the idea is kinda good.