That is exactly what Malaysian Airways has reported - there were two and only two data transmissions that they knew about - takeoff and cruise. They know of no others - the speculation is contagious.
Those engines don't transmit continuously - they transmit at significant events or every 30 minutes.
Not sure if there's a way to turn that off from the cockpit. If there is, then the hijacking theory still has legs.
If not, then there's no way to fly for 4+ more hours without that data being transmitted, and no reason (that I can see) for RR or Boeing or Malaysian Airways to cover it up.
that means nosedive or massive explosion.
That's pretty much my take on it; something catastrophic along those lines; obviously the most logical conclusion. They should be able to estimate where the wreckage is and do a thorough search and eventually find what's left. I have a feeling that there's some incompetence going on here; that people have looked in the right area, missed or overlooked things, and then concluded that they wouldn't have to search that area again.