There's no real story implications of Shangs brief change...it was just a cool effect they chose to use to make us ask these questions...this event is not touched upon in Konquest...or in Shangs ending, or anyones ending and likely won't be brought up, or referenced in another MK game...just a cool effect and a nice reference to Shangs original form

Exactly!!!

Why would it be touched on in those respects? Konquest takes place before the intro and his ending has him killing Blaze, not dying.

i think this reason is enough for this topic

they show Shang Tsung old in Shaolin Monks.When he gets souls he turnes younger.