Overwatch has, by some metrics, overtaken League of Legends in terms of popularity in Korean PC bangs.
A post that appeared on the Overwatch subReddit showed that last week Overwatch had a 0.4% lead over League of Legends, in terms of play time in PC bangs operated by GettoGold. GettoGold run around 40% of the PC bangs, a place where people go to play games in a social setting, in Korea.
More data from Korean site Gametrics, stated that Overwatch hadn't quite taken the lead away from LoL across almost all PC bangs in the country, but was within 1% of doing so. The upsurge in popularity for Blizzard's shooter meant that play time for League of Legends in PC bangs fell to a four year low.
Of course this doesn't mean that League of Legends is dead. The launch hype around Overwatch is still strong, and many people will be trying out the game in PC bangs for a fraction of the retail price, before deciding if they wish to purchase it for their home machine.