As first reported by Phoronix there was an exFAT Linux driver that was published as open-source earlier this year and it turned out to be accidentally leaked from Samsung's Android source code. But in the end the issue was rectified by Samsung officially open-sourcing exFAT Linux support even though the Microsoft file-system is riddle with IP/patent issues.
While there hasn't been much to report on in recent times, there's now a kernel mailing list discussion about getting the exFAT file-system support into the Linux kernel's staging area. Right now the technicalities are being worked out by the developers to figure out what needs to be done and whether the upstream Samsung developers can be contacted and have any interest in mainlining their former source-code. There's likely more details to report in the coming weeks.