Splintered Fate just had its first big post-launch expansion, which not only adds a whole new area to do Turtle-y battle in, ...
Casey Jones & the Junkyard Jam is worth picking up if you want a reason to return to Teenage Mutant Ninja Turtles: Splintered Fate.
IDW's The Last Ronin storyline featured a dark end for the TMNT universe that also introduced new characters who would shape a new hopeful future.