Rumours at this stage, but the discussion below is based on CAD files that have supposedly been sent to case manufacturers in China as a heads-up.
"The most noticeable change is the switch from the Lightning port to USB-C, which would mark a major departure from Apple’s proprietary connector that has been used on iPhones and most Apple accessories since 2012." ... "Thinner bezels, USB-C, new cameras, rounder edges, and more…"
More photos on this Twitter page.