I cannot comprehend how some people already decided on a main. Sure, there are characters I want to try out, but I won't know if I should main them until I actually play the game. What if you simply do not "click" with the character you are calling out as a main right now?
I knew my main before they announced him. I understand some people waiting until the game comes out but some of us just have a favorite character (for various reasons) and they will play that character more or less regardless.
Mk9 was the first time I every played a fighting game competitively. Reptile was my favorite from back in mk2 so I naturally gravitated toward him. His play style (thankfully) meshed perfectly with my own personal style. Luckily it appears as if they are trying to give him that same play stytle in mkx.
I wouldn't have made a demo for MKX if I was Boon either. Demo(s) are for games for which fans needs convincing. It's part of marketing. MK9 needed one because the franchise had lost it's way and was finding it's feet again. For a game like MKX it's unnecessary.
I think since I've never played an MK game seriously I just don't have that connection to a character or style of play yet. I don't doubt that I'll be able to once the game is out, but or the moment I do feel similarly