Usually, SDXC support can be added by firmware rather than hardware, because SDHC and SDXC cards are physically similar. The key change is typically adding support for the SDXC standard and the exFAT file system used by larger cards. Camera makers such as Canon and Pentax have added SDXC support to some cameras via firmware updates.

That said, whether it’s possible in practice depends on the manufacturer choosing to provide that update. If Leica never released firmware with SDXC support for the M9, then the camera won’t gain it on its own.

One practical note: very large memory cards are not always ideal for photography. If a single high-capacity card fails, you can lose an entire shoot. Many photographers prefer using multiple smaller cards to reduce that risk, unless they specifically need the extra capacity for something like long time-lapse sessions.