There are speculations that this rumor is managed by FOM, or at least it's orchestrated by someone from inside F1, so we don't speak about Andretti. If this is the case Merc and Ferrari are definitely in it, so they will just play along, and don't say anything.

The full premise is stupid why would anyone speak about seats for 2025 before 2024 even started. If it would be true, it would ruin the morale of Merc, and Sainz, how could you race a full season knowing nothing matters because you will move. This type of rumors usually start at the second half of the season, during summer break not winter break.