If the sale fares are actually withdrawn after tomorrow evening, and assuming that T class remains available for the flights you want, I think you're likely to see an increase to something like the current V class fares + £200 per sector + £20 per adult extra tax. However, you'd probably need a working KVS or expertflyer subscription to the appropriate level to see what the current V class fares are.

But there has often been a pattern that on some routes, the sale fares are quietly continued beyond the sale closing date (new fares introduced at the same level) so there is no actual increase in price. At a guess, this is probably to cover routes which didn't sell as well as hoped during the sale, but the extension is not marketed in order to preserve the marketed "buy now while stocks last" effect of the sale closing date.