Can't say I've seen anything about this and Ibwouldnt think it would be in their interest to just scrap it...
I believe they are pushing those on the older 40/20 service (which is 80/20 with a bandwidth cap at Plusnets end) on to a 55/10 service though.
Plusnet may well increase the price of 80/20 though and that would be fair when compared with competitors.