Final Fantasy XI is 13 years old. As is the case with 13-year-olds, Square Enix is getting a bit sick of dealing with it.
The PS2 and Xbox 360 versions of the MMO will shut down in March of 2016. Final Fantasy XI's main story is also coming to completion this year with the final expansion, Rhapsodies of Vana’diel, coming in three major updates (May, August, and November). Though its main story is ending, Final Fantasy XI will continue to run on PC.
Square Enix also tapped Nexon to bring Final Fantasy XI to smartphones, which will feature a speeider battle system and be easier to play solo, but will retain much of XI's mechanics, according to Siliconera. It will launch first in Japan and South Korea.
On top of the straight mobile version of Final Fantasy XI, there's also a spin-off, Final Fantasy Grandmasters, a free to play, mobile, apparently-not-redundant MMO set in Final Fantasy XI's world.