If Alton continue to get suitable funding from Merlin, invest in new thrill & support rides then they will be in a good position. More importantly they need to look after the rides they have & maintain them, keep them painted, no rotting stations like on Oblivion etc. And by keeping things painted, I don't just mean using the cheap job-lot of purple and green paint they have on building frontages. Using Universal as an example, pre-pandemic we were there and some refurbishment work was going on in Suess Landing - this refurbishment included painting and they had at least 20 different colour paint pots in use.
I do agree that Bianca seems to be a move in the right direction for Alton Towers, coupled with the new owners of Merlin / funding being made available, as opposed to going to shareholders. A lot needs fixing at Towers - those of us who have worked there and seen some of the behind the scenes "infrastructure" will know it dates back to when John Broome was in charge.
Alton Towers / Merlin have got a probably got the best part of 8yrs until Universal could be a reality & threat. They [Universal] have bought the land, but are still considering their options. The planning process for a new park will certainly be a protracted one & will end up going to appeal & then possibly being called-in by the Secretary of State. There will, without doubt be a good band of local NIMBY's who won't want the Universal park for varying reasons (normally destruction of natural habitat / traffic / roads infrastructure etc). Epic Universe construction started in 2019 & it's due to open in 2025 (admittedly work did stop for a year due to Covid pandemic). So a protracted planning process + a 5yr build. Towers are safe for the time being but should not be complacent. Universal would build highly immersive thrill rides & attractions like at their other parks & they have the IP rights for Harry Potter, which is a licence to print money.
A good case study / example to use on the likely length of the planning process is Center Parcs Woburn (as the local planning authority was Central Bedfordshire Council**, so possibly the same one Universal will have to deal with). Center Parcs announced the project in 2004, with plans to open in 2008. They spent £5m on just getting the plans approved (lots of local NIMBY's had the planning application called-in to the Secretary of State). The village opened in mid-2014, so ever so slightly delayed. NB: ** = this is what the council is called now, it wasn't at the time of the application - there have been local authority changes in Bedfordshire.