If this is announced, and not undone within 30 days, then the market is true
If the show moves to another venue/channel/host/etc. but aren't on comedy central anymore, it resolves true
If the creators voluntarily stop making the show, it resolves true
If the show changes names but still has at least one of the two founders associated, this does not trigger a resolution to true
If the show transitions to a new form, but there are still episodes featuring new content, it does not count as being cancelled.
If the show goes on hiatus and there is no new content for at least a year, the market resolves true.
tl;dr if new official South Park content is being stops being produced regularly, the market resolves true.
Comedy Central could cancel the show if SP starts doing inappropriate or controversial content, like mocking religion or if one of the characters uses the N word.