The most likely doctrine to change:
607
It's a tough one - it will result in some bleed-out when they do it. But once the dubs accept the foolish re-applications they apply to the 'Gentile times' and the dates that depend on that date, they will have unshackled themselves from the most notoriously false insistence they use.
Within 5 years they will have forgotten that they ever believed 607. They were able to unleash themselves from a more currently critical doctrine IMO with the 'Generation' changes. Most Jw's did not blink. I did, and in time it helped me to leave as I unraveled the skeen. But most Jw's did not even notice for all intents and purposes.
Once 607 is dethroned, with some insistence that we can't mark the 'time of the end' by using 'foolish chronology' like other's attempt to do, and then gently blaming all the flock for having misinterpreted what was stated in the past, they will be free to claim that they don't set time or dates.
The absolutely least likely doctrine to ever change:
Disfellowshipping and shunning practices.
This is the Damacles' sword they use to hold the masses. They can change anything, and if someone objects, they loose their entire social and family network. You control the masses by threats and coercion, not by holding to any eschatological dates that can be shown to be wrong in time. Most cults learn this lesson in time.
Jeff