There soon are no people to enjoy the difficult content, because they are dumbing down the content where you should be learning your class and basic mechanics. There's less and less motivation to get better. HC progress guilds are already complaining how difficult it is to find competent recruits. Not many new players or returning old players care to get into raiding because face the facts, LFR gear is not much worse than normal gear. The problem is the lack of motivation. Heck, you can complete the legendary quest chain in LFR. That's just wrong.
E: The gap is there, but nerfing normals or making LFR harder are not the answers. There should be more motivation to move from LFR to normal and then to HC. Firstly, LFR gear should never have higher ilvl than previous tier's normal gear. Top of that, maybe make an end boss or even wing end bosses not available in LFR. Currently new player's personal PvE progress is: Level to cap. Reach ilvl to 5 mans. Reach ilvl to LFR. Complete all LFR and see the content. Ask yourself if you want to get dedicated to see higher numbers. That's pretty much it.