Unlike JB, I believe this was written before 70AD, to the Philadelphia Church, in a time intense persecution from both Jews and Romans (namely Nero). Jesus was telling them to hang on, persevere in the faith, for victory and relief was coming (quickly). Before 96AD, the "synagogue of Satan, who say they are the Jews" (verse 9) was dispersed/destroyed at 70AD, so that is only one of the reasons this can't be for Christians living @ 96AD. Also, persecution of Christians was at its peak prior to 70AD, not 96AD (I'm not saying there wasn't pockets of persecution here and there, but no where near as much prior to 70AD, Read from Acts 6 onward and you'll see how the Jews went after Christians).
We can draw application from this, in times of persecution we can trust God as our deliverer, even up to and in death.
BTW, the world used for world here is Oikoumene, G3625, it doesn't necessarily mean the whole entire world....
#3625 οἰκουμένη oikoumene {oy-kou-men'-ay} feminine participle present passive of
G3611 (as noun, by implication of
G1093); TDNT - 5:157,674; n f
—Greek Word Study (Transliteration-Pronunciation Etymology & Grammar)
1) the inhabited earth 1a)
the portion of the earth inhabited by the Greeks, in distinction from the lands of the barbarians 1b)
the Roman empire, all the subjects of the empire 1c) the whole inhabited earth, the world 1d) the inhabitants of the earth, men 2) the universe, the world
Same thing with EARTH, G1093, can be and should be in this case interpreted as "LAND" IMHO.
#1093 γῆ ge {ghay} contracted from a root word; TDNT - 1:677,116; n f
—Greek Word Study (Transliteration-Pronunciation Etymology & Grammar)
1) arable land 2) the ground, the earth as a standing place 3) the main land as opposed to the sea or water 4) the earth as a whole 4a) the earth as opposed to the heavens
4b) the inhabited earth, the abode of men and animals 5)
a country, land enclosed within fixed boundaries, a tract of land, territory, region