Imac, are there any chances that you will upgrade bootstrap to 3.x.x in future releases? If yes, could you give any ETA?
Jacek,
No such plans yet.
Please let me know why do you need Bootsrap 3.
Thank you for your answer.
1) Bootstrap 3 utilizes mobile first approach. It's 2015, over 70% of web traffic is mobile and there are many enhancement for mobile devices. There is definitely better grid system which allows you to take better control over how you store looks on different devices.
2) Community and popularity.
Bootstrap 3 gained such a popularity that it became a standard framework for many solutions (e.g. ASP.NET MVC). The web is full of many free code snippets, templates etc. for Bootstrap 3. Why is it important? Well, if I start a new shop the most important factor for me is time to market. If I want to quickly start a new shop I should be able to have all the basic customization done as easily as possible. I should be able to go to:
https://bootswatch.com/ and replace my bootstrap.min.css with another one in order to change template colors. Also I should be able to do some minor modifications by using e.g. bootsnipp.com
It's also easier to find a front end developer who can adapt the ready bootstrap 3 template to cs-cart. More developers = more cool templates, feateures etc.
To sum up, it's not the matter of utilizing the power of Bootstrap 3. It's the matter of utilizing the power of community which stand behind the Bootstrap 3.