Based on previous GTI launches, it’s usually launched a good few months after the non performance models we probably won’t see the mk8 GTI until well into the second half of 2020 and as Guzzle has said, you’re unlikely to get discounts in the region of £6k.
Additionally, if demand exceeds supply, or of VW restrict the number of GTI’s they build in the early part of the car’s lifecycle (they’ve had a tendency to do this in the past), then customers can also look forward to long lead times between ordering and getting their cars. With the mk7 GTI, it wasn’t uncommon for some of the early GTI customers to experience a wait of 8-9 months.
@Plodalong; if you wait for the mk8 GTI to be launched and order one, it might be well into 2021 before you get it. Only you can decide whether to keep your existing car for a couple more years and be an early adopter of the mk8 GTI or take advantage of the £6k discount and get the mk7.5. Not a bad dilemma to have though!