Some speculations:
First of all, X is
not set 15 years after Ginga's event but 15 years after the defense team XIO was founded to fight against monsters transformed by Spark Dolls. It is still unconfirmed whether X takes place in Ginga's universe. It is very possible X is within its own universe given that none of the previous actors/actress are returning.
The main theme of this series is Cyber/Artificial Intelligence/The Forbidden Technology.
Throughout over a decade of harsh battles fighting against SD monsters, XIO has developed various weapons in eliminating its enemy. After 15 years, XIO is still thriving and its technology continues to advance. One of the major invention is the CyberCard (CC) series. Each CC contains the power of a mortified SD monster. It appears XIO would create a CC after defeating a SD monster. This power is to be used for arming Ultraman X (Could X be a cyborg created by XIO?).
Another XIO's powerful weaponry is this Ultra Booster/Ultra Raise, a device can analyze Ultraman's power and shot beam similar to Ultra's
The main gimmick of this series is based on a unused concept originally designed for Ultraman Max:
In many series, humans have tried to acquire the great power of Ultras and Monsters. Many times such attempt would backfire.
Will XIO's technology result undesirable consequences?