You would expect someone like me to put 'decline', but it depends on personal interpretation. So I went for stagnation.
My theory is that it couldn't really get any worse. We hit rock bottom in 2016 and 2017, and again these past 2 seasons. It could get worse of course, and I expect a number of things will continue to decline. Events and opening hours have been wound back down and I think this will continue, as will street theatre and I can see the monorail going. That's all pretty grim stuff, and I doubt I'd really bother going much after that. Maybe a visit once every few years to see what's new. Very sad.
So with that grim assessment, there is a reason why I put stagnation (optimistic at best). When they were scraping the barrel in 2016 and 2017, the only real positive coming over the horizon was Wickerman, which would have just been pretty much standard periodic investment in years gone by, with everything else was pointing in the direction of everything that's happening right now actually. Its around that time that the fate of the monorail, the spa, and the current Skyride closure was sealed. The difference now is there is some sort of partial rescue plan in place whereas there wasn't before. The problem is that in putting out fires, new ones keep cropping up elsewhere.
I think there's signs of this already, but from a business point of view I would put my money the park being a slightly tidier version of what it is now with a few extra flats and maybe a major investment. Opening hours will continue to be poor, I can see another event going. Maybe we'll get some more interesting food options will come forth, but the core offering will remain crap. Investments will be probably be better than the cheap tat like the Walliams World fiasco, but a far cry the what we saw in the 90's. They'll mainly be replacements of things reaching end of life and not additions. I can see operational costs being cut further. Sadly, the Monorail is a gonner.
I can't see the business case for high levels of investment, and if Blackstone thought it was worth it, we would see some green shoots by now. But money appears to be being spent on stopping further rot. We're in a new normal, it's a regional park of 2-2.5m visitors per year mascerading as something better by riding on the name recognition of past glories and will remain that way.