I'm in serious research over the '16 Ford F150 Eco-boost platform.

If the chain (or rubber belt) should break, does the engine just die and come to a stop, or does the pistons slam against the heads and destroy the valves and the heads before coming to a stop....???

 

2.7 or 3.5?

Both are chain drive.

Earlier model 3.5 issues:

Ford F-150 ECOBOOST 3.5L Engine Pattern Failures

I would assume it is an interference engine and would be toast if you lost a cam drive. However, if the timing chain were to stretch much, you will get a CEL and can read a code telling you that the cams are out of time. At that point you can a) drive it till it blows or b) have the issue corrected.

With proper oil changes, that would probably be north of 200,000 miles.