There definately won't be any issues regarding the space required to put the movies on, just like if they tried to put movies in MKD, they'd would have had the space to. However, FMV endings are a lot of development time and money (due to the need to make them look even better now since the next MK will be on next generation consoles) and more likely than not it'd detract from time given on developing the gameplay itself.

If you remember the endings in MK4, they were also very brief. While I don't want to say that some of the text endings aren't brief as well, cause they are, however a lot of the text endings convey a lot more story than the MK4 endings. If anything, I think the text endings should be lengthened to at least double or triple the amount that MK usually gives out from now.

^^as said above, text endings are better for the story, which is about 60% of the reason people play the game in the first place....i'm a huge fan of the mk mythology and don't want a stupid fmv movie showing more polish than substance(cough cough tekken cough)

If the voice acting is anything like Konquest mode then no thanks