The HDMI ports are strictly used for stacking.  I'm not aware of any chance that this will change in any future firmware updates.
I assume it's no, but worth asking...  maybe it can make it into a future firmware... On the 5548 is it possible to treat the hdmi ports as standard ports instead of using them for stacking. For various disaster scenarios (including paranoia from experience with a different vendors handling of a switch going down causing the stack to fail instead of just the unit), better staging of rolling updates, etc, we want the switches to be separate (each having it's own IP, etc...).  It would be nice to still make use of the high speed hdmi ports as a LAG for switch to switch interconnect instead of treating two switches as one.
Can HDMI ports be used outside of stacking