What exactly is your question?
Whether they will return as melee ADCs?
What is your criteria for a melee character to be considered an ADC? (Without knowing that, I don't know how anyone could answer your question...)
And just saying "People picking them as the ADC in bot lane" or something doesn't really shed any light--what changes would make YOU pick a melee as an ADC in bot lane?
My guess is that the reason melees haven't been viable as ADCs for a long time is that balancing them as such is either extremely difficult or impossible.
If you have a melee with massive sustained damage, there are several problems:
- How can they stick to the target long enough?
- How can they get to a target without being smashed by defenders?
- What happens when the enemy team turns on them?
With assassins, they have a way to get in fast, dump their damage, and get out fast. With an ADC, you don't dump damage--you stay on a target dealing big damage, but over a longer period of time.
With casters, you generally either have some range on your cast abilities, or some sort of good CC that generally lets you dump your spells. Then you back off and wait for the next CDs.
If you have a melee that can viably get into a fight, get onto a priority target, stick to that target, and not be instantly blown up by the enemy team (you will be in range of the entire team if you are melee), my guess is that you would be impossibly OP. How would you stop such a melee ADC? What can the defending team do?
With a ranged ADC, you have several interactions possible:
- Chase them out of range with bruisers/assassins/etc. They dive at you, your team may or may not peel them, but regardless, you (as the ranged ADC) have to back up a bit and start focusing the diving people instead of the enemy carries.
- There is a lot of positional play because you have range.
- If a target needs to get away from you, they can run while others intercept you.
With a melee adc, many of those no longer work, or work too well.
- People diving the melee adc? Well, because they are melee, they won't have a team ready to peel for them; they will be at the very front line. Even if they turn on the divers and leave the enemy carries alone, the enemy carries (if ranged) can focus them while they are busy with the divers.
- Not much to do in terms of positioning--either you are at point blank range attacking someone, or you aren't.
- If a target needs to get away from you, they try to run. You are melee--so either you have some super stickiness or you don't. If not, you'll never be able to stay on targets. If so, the only way to stop you from sticking to someone would be peelers.
I think the main thing is that as a melee adc, you have to run into the thick of battle and STAY THERE to lay down the dps. You can't just get in, dump, get out. You can't unload a rotation of spells from short range and back off to wait for CDs. You have to run in and stay in.
This causes a fundamental quandry--carries generally build damage and not much defense. How do you stay in there without dying very fast?
If Riot gives you abilities to stay alive for a while, where is the counterplay? It seems that you either get to go in, do tons of damage, AND stay alive somehow, or you die really fast.