I'm not sure which is more important... the 1914 doctrine or the 144,000 doctrine. Take away 1914, a bunch of JWs leave, but a bunch more will stay. Changing the 144,000 doctrine, however, becomes a lot more personal
Take away 1914 and we're no longer in the last days (this "generation"), Jesus isn't ruling, and the WT wasn't chosen as god's spokeman (1914 is critical to establishing 1918/1919 in WT timeline).
Take away the 144,000 doctrine and most JWs don't give a damn...because they aren't going to heaven anyway. What do they care if one or 144,000 are going to heaven? 8 million JWs aren't in the club anyway so it doesn't matter.
Of course, all this is a moot point because WT made the same exact claims and attached as much importance to the year 1874.
We'll know for sure what is actually in this seven-minute video next week, but something tells me WT will still hang on to the date but present a nice song-and-dance that essentially minimizes it to a point of irrelevance. Why do I say this?? Do WT or JWs talk about 1874?