I wouldn't count on it, and if it does come out this Fall, I bet it's just a band aid version, poorly hacked onto existing Touchwiz.
Where the all new Galaxy S6 coming in March, will be fully built around Android L, and Touchwiz on the S6 officially made for the 'L' version. I bet will be different and much better than 'L' on the S5 and Note 4.