A new Idolmaster SideM Live is scheduled for next year.
Today, after Idolmaster SideM‘s special 4th anniversary broadcast, it was announced that the franchise has plans for a 4th Live, to take place in Spring 2019.
— アイドルマスターSideM ランティス (@SideM_lantis) 20 de agosto de 2018
Specific details on it are still unknown. Information on it (units confirmed to perform live, dates, locations, etc) is going to be announced via Idolmaster SideM‘s twitter account and official website.