The newly built runway will become China's unsinkable aircraft carrier

[Arsalan]

The Island may be currently a recce outpost and may in the future serve as a staging point. But I doubt that it has the space(or the size) to become a full fledged base whilst still being able to defend itself. It would be premature to say that it might become the Chinese equivalent of Diego Garcia

Its distance from main land china compared to the distance of Diego Garcia from UK/USA is also to be kept in mind. Further more, there have been rumors of China building some artificial islands in the South China Sea that will be at least twice the size of Diego so this may serve just as an outpost.