I feel that when something such as John Oliver purchasing close to $15 million in outstanding debt happens, it makes the government look foolish enough that some type of legislation will be implemented. There will likely be stricter practices involved for start-up debt-buying companies but of course this will take quite some time to occur as is usually the case.
His piece was about how little regulation there is currently governing that type of debt-buying. He even highlighted an Arkansas government meeting in which they passed a law making debt buying/collection easier for banks, all the while joking that the sponsor's wife worked for a bank, and they should help keep him happy by keeping her happy. Unless there's a giant public outcry or some sort of lawsuit, I doubt more regulations will be forthcoming.
This question really asks to predict the future, but I will assume it means "do you think..." I don't think legislation will come out of this act. Forgiving debt, especially medical debt, is something that can help the country. If a company is willing to help to economy by doing such an act, I think they will not be investigated.
Legislation making it tougher to enter the debt collection industry is unlikely, even after John Oliver purchased nearly $15 million in overdue medical debt. Although this showed how easy it is to enter the industry, there is little political will to take the issue on. John Oliver previously showed the ease in which one could form a church, and nothing came of it.