Riot Games announced they will release Teamfight Tactics Mobile in mid-March 2020 for most countries in the world. Furthermore, it will be made to accommodate the veterans from the get-go and offer the newcomers a huge player base to matchmake with.
Teamfight Tactics Mobile is coming in roughly two months but the best part of the news is probably that it will feature cross-play with PC. Not everything is perfect though, and just like the release date will not be in mid-March for every country in the world, the same will go for playing with the PC players.
Namely, the launch will happen on the same date for most countries and cross-platform play will be available in most regions. Therefore, the release date and cross-play may both be available to you immediately, one of them might be amiss or neither will be in mid-March, depending on where you live.
While the veterans will have the upper hand since they are more used to TFT mechanics, thanks to the months of gameplay on PC, Riot Games made sure the playing field will be as level as possible as TFT champion Set 3 is going to pop up at the same time. Therefore, while the veterans might have an easier time learning the champions and items in search of the most optimised compositions, they will still need to go through the learning process along with the newcomers that install the game for the first time.
Both iOS and Android will be supported but the hardware requirements have not been listed yet. Considering neither League of Legends nor Teamfight Tactics are taxing on PC hardware, it is highly possible most contemporary smartphones will be able to run TFT Mobile.