The other factor that argues for the 300-350 mile range version being the initial release version, is weight. Tesla has never released a light vehicle with such a large, heavy, battery (around 190 kWh). The release version of the Cybertruck will be extensively tested by automotive journalists, etc, and the off-road capabilities and on-road handling dynamics will get more favorable reviews if not carrying excessive weight.
Even if supply of 4680 cells is not a constraint, Tesla may very well release the 300-350 mile CT first, so it can get more favorable reviews. I have multiple CT orders to cover all my bases, but the first one was the Dual-Motor 300+ mile version because a lighter vehicle has many advantages for my uses. I also want a 500-mile version!
There are also good arguments to release the 500-mile version first, we will just have to wait and see how Tesla handles it. I'm leaning towards guessing a 300-350 mile version.