After a very short Steam Greenlight campaign of only 8 days Superku has actually been greenlit! Much to my surprise but thanks to all your great support! And thanks to Valve for greenlighting the game too, esp. because it had not made the top 100 yet!
The roadmap for now is to work on the remaining 7 levels first, then start with sound and music design and polish the game for 1-2 months afterwards. This results in an estimated release of early 2016, which is convenient as (to my knowledge) January-February usually don't have that many game releases.