"Every other rh based distro got newer packages with docker/kubernetes!"

This not the case. Even redhat has older packages of docker. Older does not always mean outdated. Alot of updates get done via patches, but this results in a minor version updated of the current package. Official docker latest is 1.12. You can install those and then build kubernetes from source. Takes a but of time, but then you have the latest greatest software. 

Scientific linux follows the redhat sources. Extra packages may be available through EPEL and such. A good point you make is, "Is it possible to update them(in sl extras)? Can I help with that?"

Create updated packages and put then in EPEL repository.

Custom installation:

Follow these instructions to configure docker and kubernetes

1. Install docker: https://docs.docker.com/engine/installation/linux/rhel/
2. Install ectd
3. Install flannel: https://github.com/coreos/flannel
4. Build kubernetes: http://kubernetes.io/docs/getting-started-guides/binary_release/#building-from-source

Result is docker and various kubernetes docker containers and images, which have to be configured to your liking.

Then test your result. 


Also, there is Feroda linux, which is redhat community latest greatest distro. 

Hope this helps you in making a decision.