The entanglement theory would imply that if you build a detector that turns the gravity interaction into a finite piece of data observable by an (amplified) system, then gravity will act as an observer and collapse the waveform when it reaches that point. That's my take on the whole thing... It's almost like information theory. If the information is lost to the sands of time (below noise floor if you will) then the entanglement can continue.

From my recollection of Hawking - it’s the energy of light that disturbs the particle being measured thus confounding the measurement

Presumably a gravity based detector would have similar issues as these particles are affected by gravity (as can be seen around black holes)