Yep, they'll get caught. Last season, Riot didn't seem to really crack down on it until later into the season, and I'm really hoping they'll make a push to crack down on it here in the first couple months of this season, too. People tend to feel a lot of pressure to do well in placements, so they seem to be a popular time for people to get boosted. On top of that, the soft reset results in a lot of people dropping a significant amount in rankings. It'd be very tempting for somebody who maybe worked hard to hit G5 last season, only to place into S5, to get a friend to pull them back up to where they left off so they don't lose all that progress they had made the previous season.