Yes = Kylian Mbappé is a Manchester United player by the end of the January transfer window.

No = Kylian Mbappé signs for another club/stays at PSG.

*For the market to resolve yes, the deal doesn't necessarily have to be fully completed by the end of the 2024 January transfer dead line, it just has to start within the window and for Mbappé to then be an official Manchester United player before the summer transfer window.