There needs to be a formal coalition, e.g. tolerating a minority government does not count. I will follow the mainstream media consensus on whether a formal coalition exists. Generally, this involves things like a coalition contract and a division of the cabinet positions.

There are currently six elections planned on state level in this timeframe (https://www.wahlrecht.de/termine.htm) and also some states where the state of the parliament seems somewhat unstable after the elections last year.