Me-thinks that though they haven't done anything yet, given the sheer amount of Ship Tease between them, at some point after the series ends they will end up together. I believe they are just simply unaware of their feelings for each other as of right now.
That would be understandable given they're both teens (exact ages unknown, though I believe around 15-16) and they were in a violent feud with the Witches and with a Kishin.
soul is waaaaaaaaay too good for maka. he would never like her. soul protects her because its his job as a weapon. and aren't they being controlled by madness in this pic? also, theres something called, "fan service" like the soul and black star moment. or the similar one that happens very briefly between liz and patty on the nidhog. (the ship) and do you think that liz and patty would ever, "do something"?
"what are you smoking? don't you see how cool i am? you think a cool guy like me would settle for a flat chested girl like her?"
i quote soul, speaking to spirit about maka. from the real anime.
Actually, in all reality, SOUL is not good enough for MAKA. She is a one-of-a-kind meister that could, if she tried, resonate with any weapon. Though he is one of my fav characters, he really cant do anything without Maka. Because of his black blood, if he were to find another meister, he would need to find another with a powerful Anti-Madness wavelength, which is very rare. Also, he is EXTREMELY loyal to Maka. You dont risk your life like that MULTIPLE times because its your 'Job'. Do you ever see Liz, Patty or Tsubaki jump in front of a fatal blow for their meisters? Nope! Its obvious that Soul cares for Maka greatly! And there is SOOOOO many obvious moments throughout the anime and manga. I also get the feeling your one of those people that pair their OC up with a main character...
Actually, they ARE discussing about using the madness in this pic. They HAVEN'T controlled by it yet. And, just to let you know in case you haven't, in the manga, Soul displays the irony of his own remarks about her being flat-chested during the beginning, turned out that small-chested girls like Maka are the kind of girl that he finds attractive.