If they are of the opinion that they should bleed every asset dry then we will see more cutbacks.
This is true, but I can't see it being likely. I think your hope about "if they understand happy customers = more profit" is the more likely outcome, or at least, I hope so too.
Surely it comes down to shareholders wanting maximum long-term profit? In which case, they must realise that the current strategy isn't working. They only have to walk into Thorpe to realise how dead things are, or Alton/Chessington to realise how much needs fixing. Or simply look at AT's Facebook page, which is covered in more complaints than perhaps any business I know.
In regards to Nightfall's question - again I shouldn't have referred to new owners, but new shareholders. Increasing shareholder value is quite different to maximising profit: maximising profit seems to be an altogether more short term vision (as Merlin are doing now), but maximising shareholder value tends to focus on creating maximum long term revenue and increasing the value of the business, which will increase share value and therefore shareholder benefit.
Wikipedia has a fairly interesting quote on its "Shareholder value" page:
Short term profit maximization does not necessarily increase shareholder value. Most notably, the competitive advantage period takes care of this: if a business sells sub-standard products to reduce cost and make a quick profit, it damages its reputation and therefore destroys competitive advantage in the future.
I would argue that we are seeing this now: Merlin's need for rapidly increasing profit margins is ultimately harming each business they own (and therefore their reputations) - this is clear from the lack of maintenance/operations spending and the forcing of cutbacks on the parks; and the reaction on forums such as this and the parks' Facebook pages is clear of the reputation problems that are growing. I think you could also argue that the competitive advantage of AT is being eroded by poor management and customer satisfaction, while Drayton and Blackpool are increasing their guest satisfaction simply by improving the park aesthetics, atmosphere and maintenance. Drayton seem to have shot themselves in the foot a bit by increasing the price too much whilst at the same time throwing a parking charge into the mix, but that's their own fault. Also, problems are perhaps less for Merlin around London where they have a near monopoly.
I think the moral of the story is - if (or when) Merlin float on the stock market, they will see significant investment/buying of shares by people who want to see the growth/profit margins maintained in the long term - many years - rather than just focussing on a seasonal basis.
With this regard, we can hope that the business strategy of Merlin parks will change. Even if things don't happen overnight, I think that shareholders would look at a park like Alton - the biggest and most successful theme park in the UK - and question why guest numbers have stagnated for the last few years, especially after allegedly the biggest investments in the park's history (although we could argue that in real terms the investment in the 80s was much more, and publicised investment figures for the last 5 years have been vastly exaggerated for marketing purposes). One would hope that with this in mind, management would have to consider reasons why visitor numbers weren't increasing, or why they aren't retaining the visitors they can initially attract with new rides etc./cheap deals.
The obvious conclusion, which I hope they come to, is that there is more to theme park success that just whacking in a £10 million ride every three years, marketing the crap out of it and hoping for the best. The theme park experience, if well executed, should see guests wanting to return in the same season even if nothing new has been added, because they have enjoyed their day with no problems, all rides open, everything looking its best, everything open when they want, entertainment when they want, and the bare minimum upselling because guests will much rather part with money when they feel they are not being forced/when they feel it is their choice. I genuinely feel the parks could make much more money if they didn't buy these hugely expensive attractions on a three year cycle, but instead spent three years making sure each guest was having the best experience possible and felt absolutely fine about parting with their money. If this were the case, they would retain the majority of the guests that had already visited, and any extra gained through marketing would increase guest numbers, revenue and therefore profits. The short term effects of this would likely be small, so Merlin understandably are probably very reluctant to try this out - after all they want those big annual report headlines of "a billion new visitors! a trillion more pounds! slightly more profit! slightly closer to world domination!". But after the float, it is very possible - even pretty likely - that new shareholders in the company would want to see their investment go very far indeed, and not spent on short term, expensive attractions which act as a stopgap against diminishing visitor numbers. Hopefully.
Hey - maybe I have this completely wrong.