Been here before
In most of the cases being discussed here, the crew elected to return due suspicion of damage. However, does anyone recall the China Southern A340 that staggered off a certain LHR runway with a tailstrike about five years ago? The crew were informed of suspected tail strike by ATC (runway lights damaged) and yet elected to pressuriase the hull and continue on an 11 hour sector to home base.
A creeping structural failure could have led to airframe failure at any stage- and Nevil Shute and Ernie Gann would have been proven correct all over again...
Surely, if there is any suspicion of very late rotation with possible tail strike, the aircraft should be de-weighted in the hold and then landed at the nearest runway - possibly the departure point.
So the multi million dollar (repair) question in this case, is, did the crew have any knowledge of the event or an event that might suggest such?
If they did, why did they not make a fuel dump and precautionary landing, and if they did not, are they not lucky it did not pop a plate or a pressure bulkhead way out over the Pacific....
As usual, it has all happened before. Have we learned anything yet ?