No. MK is it's own world and setting, and I don't see how established characters from other games/series's would fit right.

Personally, I never really liked Spawn/Link/Heihachi being added to Soul Calibur. Spawn was only put in due to a marketing deal with McFarlane, Heihachi's another Namco character (and Yoshimitsu also appears), Link, god knows what he was doing there.

I don't think bringing an character from other game, will be a good idea. MK's own characters are good enough for me.

Only if it is a character from another game that:
1. would be in a location where mortal kombat would be
and 2. if it was a very small role character, one that wouldn't play a big part in anything.

MK has enough characters they should save memory for. I say don't bring in other characters, but bring back some of the old. Like I would love to see Rain in the next MK.

I would like to see characters spawned from Greek Mythology. Characters such as Achilles or Hercules are good examples. Although I would not want Achilles or Hercules into this game, the inspiration of thought for a new character based on them would be neat.

Imagine a 7 foot Cyclops in Mortal Kombat? I think a creature like that would fit well in the Mortal Kombat universe.

Have more asian style characteres in this game aswell. I think another Monk would be neat to see in Mortal Kombat. Or a fallen Monk who is seeking redemption by going on a quest for enlightmen in other realms. It is just an idea.