what happened next?

Yep, Dickens says that he became a good "master" (boss) to Cratchit (and possibly to other employees) and that he and the Cratchits lived a happy life afterward. A friend of mine once speculated that Dickens' use of the word "master" may have suggested that Tiny Tim eventually became his apprentice, to look up to him as much as he himself looked up to Fezziwig.

I like to think that the reformed Scrooge would be shrewd, but not cynical; goodhearted, but not a pushover.

Unfortunately Waterhouse's comments are just an attempt to use the story for political point scoring. Dicken's wasn't an idiot. He had an awareness of exactly how important the money generators were to the political system of his day but he sought a more paternalistic approach and recognition of the dreadful plight of the poor at that time. His ideal would have been that, as stated above,the business continued but with a more humanitarian based approach and a recognition that no man or business works independently of the people around them. Dickens was not above the harshness of the world however and we must remember he needed second thoughts before writing in the words 'who did not die' about Tiny Tim.That's not in the original manuscript.If this was a longer novel he probably would have spelled out that they had a long and happy life, he usually did, and suggested they all died as old folks rather than prematurely. That was his and the Victorian world's best hope.