Nemesis will not go nowhere. In terms of an asset to the business, it is huge in that it will keep the guests coming year on year for another ride. You can't replace Nemesis, ever and this is not from the heart, it's physically! What do you put in Nemesis' place in a custom corner of the park. Nothing can beat it IMO for the work already achieved. It's been highly placed in the roller coaster ranks for years and continues to do so. YESSSS so many new coasters are coming about our days but, this is Nemesis and she punches well above her weight.
For Merlin (or whoever owns the park at the time), they'd be daft not to invest in a retrack when it's due, or even a slight professional improvement where suggested to get more out of her.
It's really here to stay. If you thought the Corkscrew put Alton Towers on the map, then that has nothing over what Nemesis has done for the park (and the industry), however in this instance, 28 years on and Nemesis will still be riding and not sitting prominently at an entrance as a piece of artwork.
2019 and Nemesis sits at number 16 of the worlds top steel coasters. Sez enuff like!