I posted on the Fiio forum and though they did not answer my question directly ,what they did say leads me to believe that any limit is due to the max size of the micro sd card available.  Not due to limitations on the part of the X5.  So, SanDisk has a 200gb card available now.  I'm going to...

I hope by final you mean final version of the2.6 update and not final update for first gen X5.  What happened to the promise for expanded sd card capacity?  One of my main reasons for purchasing this player was the promise of future supported capacity for sd cards larger than 128gb.