Nintendo has to reveal their roadmap for the fiscal year 24/25, which has started April 1, 2024. They will mention in their fiscal report to investors, if or when they plan to release new hardware until March 2025. The fiscal report should be during the first weeks of May '24.
The real hype for the next console will start as soon as they show new games for the next console (for example a new 3D Mario). The official console reveal (and a showcase of new games) should be about 6 months before the release.
For the current Switch I expect a direct in May/June to show upcoming games for this year. We already know that Paper Mario will be released in May and Luigi's Mansion 2 in June. Although we only see remakes or small titles this year, the constant first party software output is quite impressive for Nintendo. They usually let their current system fall like a hot potato in its last year before the successor's launch.
