People are taking educated guesses, your home island is largely supposed to be cleared using recruits, militia, longbows, soldiers and cavalry. Changes will probably go unnoticed until maybe sector 9. The lower adventures such as Island of the Pirates, Dark priests and Tropical Sun will see some slightly heavier losses but nothing game breaking. But when you get into the realms of Epic adventures and Fairytale you going to see massive changes, instead of being able to sacrifice lots of recruits your going to be forced to lose higher tier troops.
The timeline for the changes will most probably be quite long, can you imagine how game breaking it could be to unleash this amount of change all at once, BB will have to be sure the have a game that still works. Given that they introduce a lot of bugs just activating events these days I for one cannot see how these changes can take place and some compromise might take place and elements might be introduced.
The game came out of Beta testing some while ago and to my mind what has been suggested is putting it firmly back to an Alpha test state, many people will be very unhappy if they log in day after day and the game is unplayable.