I'm not sure another 1975 would work again. There's to much information online about the JW's and all their false prophecies. In fact there's so much info about the JW's online I doubt anything they could do or try would get many newbies to join. Religion is dying so it's a dead horse anyway.
What do you mean when you say "work?" I don't expect it would work to generate growth like it did pre 1975 but that wouldn't be the goal, at least not in first-world countries. In first-world countries the goal is different these days than in 1975, though. Now the name of the game is retention, not recruitment. I think setting a date would do wonders for retention - many with doubts would stick around just a little longer to see if it pans out. Once it doesn't they either leave (having bolstered the numbers much longer than they would have otherwise) or they stay and double down on their cult loyalty.
Hopefully religion and this cult continue their decline becoming nothing more than a sad stain on human history.