The expected release date will be by Spring of 2018 according to EA’s CEO Andrew Wilson during their recent earnings release. The Sims Mobile has already been soft-launched only in Brazil and Spain. On August 22nd of 2017 in Twitch Gamescom Livestream , SimGuruLyndsay of the Sims Team mentioned it will be released "later this year"worldwide. It seems the game will be a bit delayed.
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.