Given that each GUID is represented by 16 bytes. So at best there are 2^128 possibilities = 3.4028237e+38 possible GUIDs.
Will it be possible that it will all be used up?
No. Even if you assume extremely high usage of GUIDs in some area, and extremely long time scales, the key point about GUIDs is their uniqueness. As soon as you start to get repetitions with any probability that is of practical relevance, people will stop using GUIDs, and therefore won't use up any more of them. Sure, they might use some numbers which look like GUIDs in some areas, where sufficiently low usage can still help ensure local uniqueness, but those would only be LUIDs, and with a bit of luck people will also call them this way.