> USFS may change the lottery portion of obtaining reservations at some point in the future, but that the current system of showing up the day before at the VC, at 11AM and 2PM for cancelled/no show slot will remain?
Yes, that is the way I understood our conversation.
> Or will getting a walk-in permit the day before also change?
They are not talking about changing that process.
> does it mean that one would have to purchase a slot due to cancel/no shows?
That was not part of the discussion. However, even as things exist now, you can purchase a permit reservation after the lottery, but up to two days before your hike, by calling the Wilderness Permit office, IF a slot is available.
As for no-shows, there is no way they could sell those, since they are unknown entities until that 11 AM / 2 PM time, and with those, you have to be at the Visitor Center in person.