Yes, that slide is still a bit of a work in progress.
You can certainly use D3 (or any other library) alongside Ractive, though things could go awry if two libraries were trying to manipulate the same bit of the page at the same time - e.g. if an element has a style attribute like style='left: {{left}}px;' and D3 modifies the element's style, D3's changes will only last until the value of {{left}} is updated.