@Josele13 To be included in UT, it would have to be backported to all the kernels used by the devices UT supports. So primarily 3.4 and 3.10 right now. Only devices based on upstream kernel would be able to get this without any trouble.
Moreover you can also just format an SD card with ext4 if you need >4GiB files, as ext4 has a file size limit far larger than any SD card you can currently purchase.
While I'll agree having exFAT support would be great for compatibility, it's going to be very problematic to get it backported to the kernels we need to run on.