Yeah, to be honest I'm a bit worried studios might use this technology to start changing lines in already released movies, so subtly only film buffs who know the film line-for-line would ever notice.
Even done for well-intentioned reasons (like removing slurs from old-timey movies) it would open up a whole moral and ethical can of worms about whitewashing the past. And I have zero faith in studios to do it for well-intentioned reasons-- especially not when they're under pressure by religious fanatics, authoritarian governments, etc.