[ref]Nebulax[/ref], this question always recieves the same answer: It will be released when it is ready. I know exactly how you feel. I am impatient myself but keep asking this question too many times and you will be rebuked by the moderator(s).
Also it will not cost any money but [url=http://spaceengine.org/support]donations[/url] are always welcomed
I think it´s easy to make a prediction with so much margin time.
Personally if space engine will cost in steam (I don´t know), my donation will be when i will purchase the program.
I love space engine and I don't mind paying 50 €