The series has become very popular since it came out, and it may become as popular as Pokemon. The second game was released as two versions so that a child could buy one version and their parent could buy the other and both could play together.
The third game will be set in America, and it will be about the protagonist moving to America. Nintendo America has announced that it plans to translate one of the Yokai Watch games, but it hasn't specified which one yet.
The Yokai Watch toy replica was so popular that people lined up to get tickets to enter a raffle to win a chance to buy the toy.
References:
Most of the information was gathered from Kotaku articles by Brian Ashcraft
http://kotaku.com/how-yokai-watch-was-engineered-to-be-a-massive-hit-1602863085
http://kotaku.com/marvel-at-how-yokai-watch-has-totally-overtaken-japan-1638493731
http://kotaku.com/buying-japans-most-popular-toy-was-crazy-hard-1618115548
Most of the information was gathered from Kotaku articles by Brian Ashcraft
http://kotaku.com/how-yokai-watch-was-engineered-to-be-a-massive-hit-1602863085
http://kotaku.com/marvel-at-how-yokai-watch-has-totally-overtaken-japan-1638493731
http://kotaku.com/buying-japans-most-popular-toy-was-crazy-hard-1618115548