According to EB World and Noob.com, the Sega Dreamcast version of Mortal Kombat 4 is officially titled, Mortal Kombat Gold. Special thanks to Justin Cornel for informing us. Here is EBWorld's description of MK Gold.

Mortal Kombat Gold features 15 favorite MK characters plus the surprise reintroduction of several favorites. There are more than 10 interactive fighting arenas, multiple fighting modes, and several fatality moves for each character.

3000 Poly's per character

60 FPS

Dreamcast exclusive

Detailed animated backgrounds

Five new FMV's (hi res) endings.

It looks like Midway is going to be able to deliver what was promised when it was announced that Eurocom was developing a version of Mortal Kombat 4 for the Sega Dreamcast. Mortal Kombat Gold will feature everything that was cut out of the PSX and N64 versions to compensate for the lack of hardware power, and then some. From the preliminary specs given, it looks like in addition to the 15 characters from MK4, 5 nostalgic characters from MK's past will return in full 3D glory, at arcade size polygonal counts. Unlike the PC, PSX, and N64 ports, Mortal Kombat Gold will feature direct from arcade models and backgrounds with little to no polygonal reduction at all, while still remaining at the bilstering speed of 60 frames per second.
Even though Mortal Kombat Gold wasn't mentioned in yesterday's official Dreamcast US launch announcement as a release title, EBWorld has the release date set at September 9th, 1999, same as the Dreamcast's US launch date