The SDA example is perhaps suggestive of what the result would be if they altered their doctrine. I found an article from 1989 that 'resolved' the failure of the end to appear in the "generation" of the 1833 falling stars etc. Many SDA's had found ways to reinterpret the word 'generation' through the years without arriving at a satisfying permanent solution. The 1989 article simply offered that prophecy was "dynamic" and God, while remaining unchanged in his determination, can alter his specific plan at will. They used "seeming" failed prophecies in the OT as examples of this. In this way the prediction remains on the books but becomes unfalsifiable/undisprovable. Their growth since then hasn't been unusually good nor any worse than the decades before 1989. They presently claim to have about 21 million members.
The WT overlapping generations approach to resolve the same issue seems less efficient. It is similarly unfalsifiable in that it can perpetuate indefinitely, but it awkwardly strains the wording of that one passage and leaves one feeling unsatisfied and confused. The SDA approach IMO is functionally superior, in that it appears to be taking a 'rational' flexible approach to prophecy as a whole. Much harder to argue against.
I don't see much really changing no matter what they eventually do. I know I've said it many times, but IMO doctrine just differentiates one church group from other churches it's less important for recruitment or retention of membership. That is the result of a welcoming sense of community and group identity. True sometimes specific unusual doctrine becomes inseparable from identity, (like Armstrong's WWC of God with Sabbath and faith healing) and a change would precipitates a serious loss of membership. For the WT it might be their 'earth paradise' doctrine or their ant-trinitarianism. But peripheral stuff like this can be accommodated easily as the numerous previous changes in the WT teaching about 1914/18 over the years has shown.
Again, IMO, they need to address this festering wound. Either the approach of the SDA would work or some other open ended rational sounding way to diminish the importance of the 607/1914 dates is necessary.