That promise in Rev 3:10 can be accomplished in many ways. To assume it’s fulfilled by rapture is careless interpretation. It can be fulfilled by delay, and letting them die a natural death before it comes. 2 Thess clearly gives signs before Christ comes.
One more note: Paul had spent less than two months with these new believers, yet the departure event was so significant a reality they were to watch for that he had to deal with their questions regarding the event in two letters to them. That's for those who think the notion of the snatching away is not important for believers. It is the foundation of the Biblical principle of imminency.
After Rev 3:10 comes Rec 4:1, illustrating the promise of Rev 3;10.