Miloslav Mil and Michal Plandor,
@Miloslav, perhaps you should look at the HANA Enterprise Cloud Project environments to help with your development efforts and at how you can maximise the HANA platform for your app - it is a great service (which I work for :disclosure) and it is a great HANA enabler.
@Michael, If you are concerned about the HANA investment, I would suggest you also look at the HANA Enterprise Cloud to help you to determine the value case and proposition for your business needs - we have had a lot of people using the project cloud for just such a reason and yes some of them have gone into Production, others staying on premise or with hosting partners.
I don't mean to sound all salesy, I usually hate writing this type of thing, but I have seen a number of companies clarify their HANA thinking with the HEC and thought it might be an idea.
Thanks
Chris