I think it’s 50-50 that we will never find out what happened.
My working theory until something else supplants it:
The co-pilot with only 1,800 hours was part of the hijack team. The plane was hijacked but the passengers fought back, and 370 crashed into the ocean. By the time floating wreckage is found, it may be 100s or even thousands of miles from where the plane hit the water. By then the pinger on the black box is long-dead. We may not find the undersea wreckage for years, decades, or ever. We may never find out what happened. 50-50.