zero

No chance in HELL I'm sorry but there is just no way that alllll of the people ever created in MK history are all playable that is more than 50 characters.
Let the characters in it have something to do witht he story.

The chances of them all being playable is 0%. So far from the Konquest videos you notice some characters such as Mileena, Tanya Raiden,Kenshi and more I can't think of are very detailed. That is a tell tell sign that they are playable and I would think the same for characters we haven't see in Konquest that could be playable. On the other hand we have seen characters like human Reptile and MK1 Sub-Zero very low detailed, I wouldn't be suprised if these characters aren't playable.

The words "slim" and "none" ring a bell?

Too bad. Despite a strong fanbase, I'd argue that MK is on a downward spiral since the 90's. The thing that can truly revive MK on a total-gamer level would be an ultimate game, in which a storm of characters are playable.
All of you surely would like to see all characters in Konquest, even all MK characters ever, playable in the game. The question is, would the monetary return because of this exceed the effort into putting in 25 more playable characters?
As for the ninja Reptile, I sure hope he's playable. I thought he was fairly detailed in the trailer... and being such a fan favorite in particular, you'd think they'd at least make him playable after animating him.