I first do not think they will change anything about 1914 for at least 20 or more years but one day it will have to happen. Since 1914 is their meal ticket and they have it in print prior to the year happening, they will never abandon the year altogether. They have too much tied into 1914-1919 as well as have held onto it for too long. So here is my theory on what they do to change it. I use Matthew 24 for my theory.
Matthew 24:3. While he was sitting on the Mount of Olives, the disciples approached him privately, saying: “Tell us, when will these things be, and what will be the sign of your presence and of the conclusion of the system of things? 4 In answer Jesus said to them: “Look out that nobody misleads you, 5 for many will come on the basis of my name, saying, ‘I am the Christ,’ and will mislead many. 6 You are going to hear of wars and reports of wars. See that you are not alarmed, for these things must take place, but the end is not yet. 7 “For nation will rise against nation and kingdom against kingdom, and there will be food shortages and earthquakes in one place after another. 8 All these things are a beginning of pangs of distress.
I put in bold the three things that matter. What I think they will do is leave 1914 as the year Jesus was enthroned and his presence began as well as satan being cast to the earth. The problem they have is how long can the "last days" be before people stop taking it seriously. So that's really the only aspect they need to change. Since verse 3 uses the word and between presence and conclusion of the system they can nulight everyone with these being two separate events. Since verse 6 specifically says the end is not yet and verse 8 calls those prior events just a beginning of pangs of distress they can say in 1914 pangs of distress started but the last days did not.
At this point they could do a number of things, either pick a recent event and say that that is the beginning of the last days, or pick a future description of Matthew 24 that has not occurred yet and say that that event is the actual start of the last days. They could say how many of these events are taking place so we know the last days are close as well as saying that since the term "days" are used, that it would be a very short period of time. Hence they fix the 1914 problem, 607 still doesn't have to be changed, and they keep the end being imminent in the forefront. Any criticisms to my theory?