According to the newest rumors on L-rumors, it will take still a lot of time for a S1H successor. I doubt that it will come in 2025, if you read this:
S1H successor:
Panasonic is also actively exploring the planning of the follow-up products of LUMIX S1H. LUMIX S1H, as a camera positioned for film creation, has a unique position in the market. With the continuous development and changes in the field of film micro camera, Panasonic has received a large number of opinions and suggestions from all sides. In terms of product form, there are different expectations from users and the market. Some want the product to be similar to the FX3, cutting out the warship section and focusing on cinema and video functions; some prefer to keep the micro-single form while strengthening the video function; and others expect to make it a square camera similar to the FX6. In terms of functional requirements, features such as 8K 60p or even 8K 120p video shooting and built-in ND filters have become the focus of users’ attention. In order to better meet market demands, Panasonic merged with its professional-grade system imaging division in 2024, integrating the technical resources of both parties and engaging in deeper and closer discussions with technicians. Although the launch date of the next generation of the LUMIX S1H has not yet been determined, it can be seen that Panasonic is putting its best foot forward in the development of this product, and is striving to bring users an even better tool for film creation.