Follow Nintendo’s official channels or reputable gaming news sites (IGN, Nintendo Life, Gematsu). A new Mario & Luigi game has not been announced as of early 2025 (my training cut-off is 2023, so there may be newer news I missed — you can check online).
While details about the gameplay are still scarce, we can expect the classic turn-based battle system and exploration that the series is known for. The game is likely to feature: mario & luigi: brothership xci