New cards could be fun but they already gave a fair bit of powers that are well balanced. Could be hard to bring new stuff on the table.
As for new tiles, I don't know. I like the chess feel of the game, it could be more distracting then engaging to have a lot of new tiles with special effects. I didn't tried the void though. I bought it with the game and forgot it in France. I wait to have something worthwhile to add to have it sent it back to me. I'm not sure I really want to play with it in fact. Is it a good addition ?
It actually is. It's not needed for the game at all, but an expansion should be something that is not needed, but is there to add more spice to the game. Tiles and game setups like this would be great if provided by an expansion.
Quantum is designed by a Eric Zimmerman, a really smart guy who has taught game design for years and it really shows. The base game is perfect as is. But an expansion would spice the game up for hardcore fans.
But the main problem with Quantum is that it got some notable negative feedback due to component quality early on and it didn't get a lot of publicity prior to being released. This game was recently praised at Secret Cabal podcast, a lot of months after it was released, and no one knew of the games existence.