About the only thing I could really hope for would be save state support for all possible games.
Or...the satirical future, Mwahahahahahaha!!
MAME gets 6000 new 32-byte PROM dumps and decapped chips to void the current zip files and annoy the pokerom kiddies.
Shoot-em-ups moved to Shmupmame after Cave classes all of its games as 'recent' (even from 1995) and bans them from being in the official build.
A non-CPU game like Pong is added to MAME, running at 0.23 frames per second on a 4GHz Core2Duo.
MAME drops support for 32-bit builds, as the final straw for pokerom-do-Brasil (and my ageing Prescott-era Celeron at the same time).
3551 stupid gambling games, are added whilst the actual hardware remains unknown and broken (like the ARM-based video slots), along with mechanical reel games with no display, no reel strip artwork, and just a couple of LEDs in 7-segment formations (like the S-Plus someone was working on years ago but didn't add).
684 mahjong/pr0n games added to the Nichibutsu drivers in their full dithered 256 color glory.
Super Duper Hyper Street Fighter Turbo with V-Tec-just-kicked-in-Yo ROMset added, where you can do 63-hit custom air combos in 4 seconds by madly bashing the buttons Track and Field style. Apocalypse is also selectable via a Konami code and can do moves nine times faster than on X-Men vs SF, and can jump; when he lands, he shakes the ground causing anyone who didn't jump to bounce on the ground like in Mario 3, causing a free hit/combo. The drill can also home in to players who attempt to jump it if performed as a Super move, and Apocalypse can turn around so no-one can cheat by hitting him in the back of the arm and/or head.