Pope's grip on the pivotal No.3 spot has been the source of intense scrutiny for most of the year and, although he held the spot for all six Tests this summer, there are no guarantees he will remain in place against Australia.
Tuesday's decision to name Harry Brook as vice-captain for the series, a role Pope has held for the past three years, further loosened his grasp and a run of three T20s and three ODIs in New Zealand could settle things.
Bethell is on that trip and Pope is not, meaning only one of the candidates has a chance to finesse their pitch.
England's managing director Key admitted as much while insisting Brook's promotion does not mean a done deal.
"There are no other ulterior motives other than the fact that we think Harry is the best person to be the best vice-captain," he said.
"There is not an elaborate scheme where if we take the vice-captaincy off Ollie Pope, it makes him easier to drop.
"It doesn't matter if you are vice-captain or not; if we don't feel you are the right person wherever you are batting - whether that's an opener or at No.5 - we'll end up bringing in someone we think can do the job better.
"At the moment, Ollie Pope is the man in possession and we'll find out what that XI will be probably two days before the first Test. We tend to leave the decisions as late as possible.
"We'll see a bit more of Jacob Bethell in white-ball cricket. I think we know a fair amount about Ollie Pope but Jacob will continue to get experience. We'll just learn more and more the more Jacob plays."
While some decisions will go all the way to the wire, Key appeared to draw a quiet end to Chris Woakes' Test career.
The 36-year-old, who has played the role of senior seamer since the retirements of James Anderson and Stuart Broad, dislocated his shoulder in the final game of the summer against India and was not considered fit to face Australia.
And, after 66 Tests and 192 wickets, he now appears to be at the end of the road.
"He was running out of time to be ready for the start for the Ashes, then once you get out of an Ashes series you're often looking at the next cycle. So Chris Woakes isn't in our plans at the minute at all," Key said.
He also offered positive assessments on captain Ben Stokes and paceman Mark Wood, who are recovering from shoulder and knee issues respectively, with both expected to be fit for selection in Perth on November 21.
