Like closing the gate after the horse has bolted. The damage has already been done. Why does everything take so long in this country?
Putting the ban so far out means they’re going to continue selling up until the last minute, and they’ll sell at reduced price closer to the ban which will increase consumption.
The better option in this case would be an increasing tax on them to the point where they are unaffordable. Then the market corrects itself.
If (and it's a big if) the human race survives to deal with the effects of climate change, the next great battle will be to prevent waste from becoming the existential problem.