I have avoided reading fan theories but my personal feeling (I am probably not the first to suggest this) about Far From Home is that it's going to open up with the scene of Spidey on the bus from IW. his spidey sense goes off just like it does in IW, but then he looks up and there's no spaceship or alien threat (the snap erased/timeline reset). a spidey deja-vu or sorts, a memory from the time-slip. "false alarm I guess..." the bus, of course, taking him on the field trip to Europe.