Here's the actual quote(s) from the lawyer, rather than what the media twisted it to say.
He said: "The families are satisfied that no expense is being spared in the investigation into what caused the accident on the Smiler ride at Alton Towers.
The health and safety inspectorate made it clear that the requisite multidisciplinary expertise was in place.
The ride is likely to remain closed for a significant period of time – indeed it may never open again. The families are reassured that every angle is being thoroughly covered."
Which seems largely positive for the park, and Smiler, to be honest.
It will remain closed for quite some time because the investigation will take months and possibly years. Investigations like this go into extreme detail where necessary.
Finding the primary cause is normally fairly easy, but not always, and they will also look for any contributing factors.
1 fairly simple sentence, but a whole lot of work to do.
If the primary cause isn't obvious, they won't stop investigating until they know, and the ride will remain shut until the investigation is complete.
I believe the primary cause will be found very easily as they have a huge amount of data, ranging from the computers on the ride itself, through to eye witnesses (both staff and GP), and video of the event. They may even have audio from the ride camera's but I am not sure on that. I'm sure you guys will know though so please speak up.
Then once the investigation is finished, they then have to write the report, which probably runs to at least a hundred pages, maybe thousands, depending on the results of the investigation.
Once the report is finished it will probably have a list of things that must be done, as well as some recommendations.
From an HSE standpoint the ride will be allowed to reopen once the things that have to be done have been done.
Given the investment in the ride already, I can't think of anything where replacing the ride would cost less than repairing / upgrading it.
At that stage the only thing stopping the ride from opening would be Merlin themselves, and from a PR standpoint this whole thing will blow over in a few weeks / months. Merlin have operated admirably since the crash, and the media will get bored and move on eventually.
The smiler crash will become a thing of legend in the playground. People are meant to be a little bit afraid of a roller coaster, it is a "white knuckle" ride after all.