To reiterate, trading Marv and RJ does nothing to harm your longterm prospects, even if it's for nothing.
Not necessarily--given their salaries, teams might not be willing to part with nothing... they might want the Jazz to trade Marv or RJ, plus a pick, in return for nothing. Or maybe they'd want to trade the Jazz back a mediocre player with a fairly large salary, with longer left on his contract. And either of those would harm the Jazz's long term prospects.