Opera are only replacing their rendering engine with the one used in Chromium, they are not using Chromium to replace their browser. Opera's RSS feature doesn't even touch the rendering engine and is built entirely with their native widgets - but even if they were to put it into the rendering engine, RSS is just XML, and can be styled in any way they want using standard web technologies.

tl;dr: The move doesn't affect Opera's ability to put RSS in their browser.