As soon as you see the parking lot full of cars at the facility that the assembly will be taking place at, you know that you are 6 months away from the game rolling out.
You know that there will need to be forklift operators, people making wiring harnesses, assembling cabinets, soldering parts, sorting shipments, testing machines, cleaning glass, touching up paint, populating playfields, prepping boxes....
You guys can guess and speculate forever, or someone who lives nearby can drive past the facility once a week and watch for when all the workers get hired in.
Simple really.