Legally speaking, you could have legit access to the verilog by working for one of the existing licensees - eg Nintendo, chip companies, fab companies. Or by buying or otherwise acquiring (eg patent trolling settlement) a license to it from Nintendo.
It's not really likely, but it's within the realm of possibility. Somewhat less likely than legally acquired game ROMs, sure, but only a matter of degree...
Of course they won't incorporate unlicensed copyrighted things from the leak in their own code, but they don't need to.