Trailer referencing Oblivion Crisis and not anything that happened in the books
well, the trailer says something like "in the time after the oblivion gates opened", which uses oblivion only as a reference of time, not a reference to the events
The same rumor of 200 years has been going around, so I'm inclined to believe it's solid information, but look at it this way
how many people are coming into TESV after playing oblivion compared to the number of people who read the book?
if they mention lore 95% of the people don't know about, it will cause far less excitement and speculation than if they do mention something they know