The one feature I am hoping for 4K streaming support from iTunes and Netflix. It's not really so important for the laptops, but it's helpful on the iMacs.I'd say there is a zero chance of a redesign and what do you mean by features? The ports will probably stay the same and any OS features added will also be available to all eligible machines..
My prediction is that 10.14 will introduce this support, but will limit the feature to Kaby Lake Macs or later. So again, not such a big deal for the Mac laptops, but more a big deal on the iMac. OTOH, what goes along with this is the HEVC 10-bit support for non-DRM'd material, and that is also limited to the Kaby Lake Macs or later.
Which is why I suggest getting the 2017 laptops or later if video is important to the purchaser.