None. It's a maintenance patch. Major update are usually numbered, not lettered.

1.16 - System Adjustments, implementation of NM content.

1.17 - Preparation for Grand Companies, Mid-range NM Implementation.

1.17a - Fixes, fixes, fixes. It's gonna be a small patch. SMALL.


To reiterate, content and gameplay patches tend to be incremential in NUMBERS. The "a" at the end of 1.17 means it's a fix, or a progress patch.

Don't get your hopes up.