Two big "old school" events that were supposed to happened but never did, and that come to mind involved Ted Dibiase in one, and the Rockers in another.
At Wrestlemania IV, Ted Dibiase was supposed to win the tournament and the WWF championship, while Randy Savage was to win the I-C title and I believe eventually defeat Ted for the WWF Championship. But the Honky Tonk Man supposedly refused to lose the I-C title to Savage, and thus Vince instead made Savage the World Champion. Dibiase should one day beat the crap out of Honky for ruining his chances of becoming the World Champion basically. I know I'd be pissed at him for it. Ted was also supposed to eventually become the NWA World Champion, but I think his jump to the WWF ruined those plans as well. Poor Ted.
Another idea for a plan that was rumored to be a possible plan, was something I read in Ric Flair's book, though I've heard nothing about it since. Supposedly, Ric was going to possibly jump ship to the WWF all the way back in 1988 and take on Randy Savage for the World Title at Wrestlemania IV. I only read about this in Ric Flair's book, so if anyone has any more info on this story, I'd love to hear it. This could've been an interesting scenario having Flair and Savage main event Wrestlemania IV.
The other idea I had for this thread was the Rockers originally supposed to be winning and getting a run with the Tag Team belts back in 1990. Jim Neidhart's contract was supposedly up and wasn't going to resign. Vince was then going to put Bret in singles competition, and drop the titles to the Rockers on Saturday Night's Main Event. During the match, the top rope broke in the middle of the ring, and the Rockers won in a horrible matchup. Vince ended up putting a halt to the Rockers reign, returning the belts to the Hart Foundation, and the Hart Foundation continued their 2nd run as champions, with the Rockers never again getting a run or shot with the belts. Jim Neidhart ended up resigning with the WWF, and this has been kind of determined to be the "official" reason for the Harts getting the belts back (the match turning out like crap certainly helped lead to this outcome). Although I know Shawn felt that Bret and Jim pushed themselves to get the titles back, although that's been denied.
That last one was pretty unfortunate as I do feel that the Rockers definitely deserved a run with the titles. Especially Bret ended up going to singles about 7 months later anyway. Perhaps it should've been the Rockers losing the titles to the Nasty Boys at Wrestlemania VII?
Someone mentioned the feud that Jake Roberts and the Ultimate Warrior were going to embark on after the summer of 1991, which I think would've been an absolutely awesome feud, if not crazy and outlandish. The matches probably wouldn't have been too hot (although by that point Warrior could have a good match as long as he was in the ring with someone good, ala Savage, Rude, etc.), but the promos and storylines leading to the matches would've been great, as the few that they did do on Supertsars were great stuff. That could've been a good feud. But then again, we might not have gotten Savage back in the thick of things and the great feud that Roberts and Savage ended up having, had the feud with Warrior and Roberts taken place like it was supposed to.
Great topic idea here.