The pull request was sent in this morning to nuke the EXT3 driver from the mainline kernel. This follows last month's article EXT3 File-System Driver To Be Removed From The Linux Kernel that laid out the details.
Long story short, the EXT4 driver has been stable for years and is backwards compatible with mounting EXT2/EXT3 file-systems. Jan Kara of SUSE is now nuking the EXT3 driver in Linux 4.3 to lighten up the kernel by some twenty-eight thousand lines of code. There's also EXT3-specific workarounds in the kernel's VM and block layers that could now be removed too.
The pull request can be seen on the LKML. Last month when Kara proposed removing the EXT3 driver, he was met by seemingly universal agreement.