I'm honestly more apprehensive about 5-man soloq rather than 4-man, and here's why
being the solo in a 4-man premade is the most toxic thing league has to offer, we all know this. There is not a worse feeling than getting trolled and or flamed at by 4 other people on your team, even when you're in the right, just to find out they're a four man premade.
I remember at the end of season 3 when no one had yet to discover the incredible op-ness that was Kha'zix, I was playing him and built Ravenous Hydra. At the time, hydra was not the meta build on kha'zix (even though literally a month later it WOULD BE) and when they (my team, who, I would later to find out was - you guessed it - a 4-man pre-made) all saw it they started flaming the shit out of me, even though I performing well. It was a miserable experience, and we ended up losing, which only further invited the wrath of my toxic teammates upon me.
With ranked next season, however, I feel like it's going to be different. Finding 3 other people who would willing to troll and or surrender just to screw over 1 guy in a ranked game is going to be so difficult it's very unlikely it will ever happen. A single troll is willing to lose a ranked game, but a total of FOUR in one game? Not likely.
What I have a problem with is ranked soloq with a 5-man premade. I mean, it doesn't even make sense. We have an entire queue for this, it's called ranked team 5v5. Why? because it's where 5 people play ranked together as a team! Your Individual rank should determined by how you play when you go in solo; as an individual. How does it make any sense to have an entire team's performance with people who already knew each other determine each person's individual rank? Well, it's simply really. It doesn't. I believe that 95% statistic they gave us about 5-man facing another another 5-man, but that doesn't change the fact that EVENTUALLY you'll be agaisnt a 5-man premade when you yourselves ARE NOT. So not only are you put at a disadvantage, each of those people on the other teams' individual rank is getting affected even though they came in as a team together.
I don't know, I just think it's bullshit to have individual rank be affected when you queue up already as a 5-man premade.