I really doubt it. Challenge nowdays is translated to "i don't have enough gear yet, i'll come back in a few weeks". Brawlers guild for example. I was somewhat proud I completed it with 872 ilvl because the DPS requirement was too tight. For those with 890+ though it was just trivial. If they want to make something trully challenging they need to make a scenario with fixed stats like it works in PvP. For once make something that some people WILL NEVER get if they don't have the skill for it. I'm just tired of gear>skill. I know it's how the game is supposed to work but come on..
The thing that comes closer to mind is the old Challenge Mode but even then some items (blademaster trinket + agility coin) made it too easy. I can only hope they do it like that but in the end it's gonna be another boss you can trivialise with gear.