Weight of a car directly relates to speed. Lighter = Faster Acceleration (all else held equal). And for an EV lighter also = more range.
But that said, some benefits MIGHT end up downstream to the consumer but the main benefit of a better battery is lower overhead/higher margin. Neither of those will likely benefit the consumer - I highly doubt Tesla would lower the price of the Y to account for the lowered manufacturing costs. If anything, my guess is the 6480 will translate into more range. Speed is a commodity for Tesla (pay $2k for turning off accel limiter) so why would they give that away? Maybe cars equipped with a 6480 will have a speed boost2 that you can unlock for another $1k? Doubt it but maybe... IMO, the most likely scenario, from consumer perspective, is a new battery will just translate into marginally more range for those lucky enough to get it.