Samba 4.1 provides a large number of performance and feature enhancements that would greatly benefit RHS. In addition this would bring Samba in RHS closer to the main branch of development for the project which would ensure a greater access to new technologies being developed such as open source implementations of features found in SMB 3.x. However, while Samba 4 can still serve the same clients Samba 3 can, within a single RHS cluster Samba 4 can not coexist (e.g. serve the same shares) with Samba 3.
In order to best keep up with new feature development while still providing a stable product to our customers, we should begin by making Samba 4 an optional upgrade via a new distribution channel. This way customers currently on Samba 3 can continue to keep their current systems online while planning for adopting the next major release of RHS. At that time we would not longer ship Samba in the base product, and only have Samba 4 available via our new distribution channel.