Release date is unrevealed yet, but it has already been soft-launched only in Brazil and just recently in Spain. Last August 22nd in Twitch Gamescom Livestream , SimGuruLyndsay of the Sims Team mentioned it will be released "later this year"worldwide.
Since the game is currently only available in Brazil and Spain, some players from other locations use APK to play. For how to play the game on your Android phone instantly, check the link below.
Sims Mobile is not the first Sims game on your smartphone. Sims Freeplay is the first one and it was launched in 2011 ~ 2012. EA Mobile and Firemonkeys Studios developed the game. It's still available on App Store and Google Play Store.