The above image is very interesting and it is taken from a official demo video (watch below) included in a Build 2015 presentation. What you can notice in the above image is,
A new development Phablet (that may or may not come to market).
USB Flash drive support (OTG). You can now extend you storage with a USB flash drive. The video says it is limited to devices with USB dual-role hardware support, like the prototype in the image above.
A new Windows 10 for Phones build with UI changes: 4-column start screen and all apps before the bottom arrow (just like GDR2).
If you have a look at the below screenshot you can see changes in the “File explorer” with the upcoming build.
Arduino support via new USB capabilties
USB OTG, Arduino, 4-column start screen & other UI changes demo: