One Way Out 🌈 🚪— Closeted Mike Wheeler and Vecna's Curse
At the end of S3, there's an orange truck with a logo of a wheel(er) next to a "one-way" slogan. In the frame is a red crate, then blue and yellow bikes together (beside Joyce's green car). This shot is referenced in the 'one way' road sign in Mike Wheeler's bedroom in S4.
Parallels & Two Timelines 📦
In retrospect all of this imagery—the color orange, the red crate—is a part of Vecna's curse, which is the theory that Hawkins was successfully turned into Camazotz and the characters were left under a trance.
Hopper's voice-over during this U-haul scene talks about "change" and "turning back the clock," repeated by Robin in the S5 epilogue and we see Henry turning the Creel clock back in S4.
If you notice, there are two versions of the Byers and Jane moving out at the end of S3.
One version happens while Jane reads Hopper's letter—it's bright, emotional with the line "hurt is good, that means you're out of that cave," which now connects to Henry's cave.
Another version happens as a "flashback," we rewind back to the Byers moving out again but it is less bright, the kids are standing around despondent, nothing is overtly emotional or sanguine. More objective than subjective.
In this version, we see inside the U-haul and the license plate. Inside are warnings and labels about having the "right equipment," something to do with sexuality, and the plate reads "Truck 7"—Will's number ("It was a seven").
The moving box El carries is "Marshall Field & Company" that foreshadows the wilting field scene of the open gate's toxicity leaking out in S4. Then it ends with a closed door, just like Mike closing the door on his basement as the last shot of S5.
Other Meta Symbols & Foreshadowing 🔴🔵
A few other things to note is the red and blue "for sale" sign, and there is also a blue crate in Jonathan's car. There are red and blue labels on moving boxes—a red "stamp" label and a blue "cave spring" label.
There is a mattress with blue flowers that recall the blue flower on the photosynthesis poster when El and the Demogorgon vanish in S1. The monster is always related to (blue) flowers.
Overall, a lot of the bittersweet feelings and symbols recall Mike's first D&D game, which had mysterious flowers in a cave. This all points to the first version of the S3 goodbye being from his perspective.
However, the craziest thing is the wheel, for Mike Wheeler, side-by-side with "one-way," when it is later a literal sign pointing to his bedroom closet. His gay subconscious is fighting him.