There might be sales leading up to the 20xx launch dates, there might not.
Retailers behave differently. Ultimately, they've all spend $X to acquire the product in the first place - markup isn't huge by any means.
One retailer may look to recoup what they can, while they can - before the product is deemed "obsolete".
Another retailer may continue to price it at $X that they paid for it + their standard % markup.
FWIW, 20xx cards will likely be in short supply at launch - and especially on the lower end 2050, 2060 etc are still months out.
So there's still going to be a market for the 10xx cards. The launch of 20xx cards will not result in a fire sale on all "prior gen" cards..... at least, not for a while.
You'll almost...