20 years? Hmm, well, I don't shoot anything that new. LOL Serious, I don't see the need.
I guess, if I had to pick something, .460 and .454 are obvious, well, I think .454 is over 20 years old, though. Dang, well, .460 then. It does break new barriers in hunting revolver ballistics. I don't want one, just sayin'. I do want a .454 Freedom Arms someday, more for the gun than the caliber, but it also shoots .45 Colt.
I guess, even though I don't care all that much for it, you have to acknowledge how the .40 S&W has taken over law enforcement. It probably outsells the other calibers in law enforcement now, at least in this country.
I give a nit for .357 Sig. It does nothing the .40 can't energy wise and the forty shoots a bigger bullet. Necking down cases rarely accomplishes much unless you're looking for another application as with necking the .250-3000 down to .22-250 to built the ultimate long range prairie dog gun.
I think the .460 really shadows the .500 ballistically. The jury is out on the .327 Federal, but I don't know that it'd be my cup of tea until they put it in a smaller, lighter gun. It could have merit in a scandium J frame. It could turn out to be my other pick, but not in the Ruger SP101. I'll take the .357, thanks.
Hell, I don't think I have a third choice. Like I say, it could be the .327 Federal if it gets picked up in a really small, light revolver. Time will tell.