In case there are some differences between my past numbers and your past numbers of challenges, there will be 300 challenges coming on disc. All kinds of crazy challenges too. The block breaking challenges are there, but we are also looking at full on fights with crazy added rules. I think the coolest one seen in the below video, that details a few, has to be the "No Arm" mode. Just the fact that your character's arms get ripped off before the fight start to ensure it stays that way, makes me giddy like a dimwit in a puppy store.
It does look like the bulk will be just standard fights with some crazy extra rules; there are those fun little extra games. Like throw a grenade into a waste basket or shoot down the "zombie" horde from attacking you. Like I said, there are better glimpses of these in the video. As well as the one the guys from NetherRealm claim to be the mother of all challenges. I'm guessing it is a fight against the whole cast where all the battle extras randomly go off.
Before I shut up and let you hit the video though, I do want to comment on the Subzero/Scorpion specific challenge. Pretty much a fight with the two against Shao Kahn except that he changes color just like the end boss for Castlevania: LoS all of which has the same battle tactics added to it. Not sure if this was something ripped off, but it does seem a bit of coincidence that it would be the same thing and against the seeming final boss of the game. Maybe I'm just reading in too much. Or maybe the Devs just wanted to pay respects to the game.