I could easily see the VizRT stations rebranding at once - wouldn’t that be BBC News, World News, The Nations (I’d assume), it appeared some of Global News runs Viz Opus (which can do graphics) so they could be included, and what London and Salford regionally? The problem would be those extremely outdated regions that are running systems that are what 10-15 or more years old and the one or two bureaus running CasperCG. They would all have to be recoded to match.
VizRT would make it easier to supply new assets and go through testing before going to air for sure. There are those regions not yet updated that would need more time to bring into line.
Then there are the offline templates. social media video and live templates and workflows to do. Sending assets to the worldwide studios and operations. Updating the equipment vehicle wraps. The website is quite a bit larger than BBC Sport's, and the design would have to accommodate the various languages that Global News caters for.
BBC News, well BBC Global News runs advertising so depending on the time-scales those operate in, updating marketing materials is also a consideration. Then there may be new formats and strands they plan to launch alongside any re-branding - architectural or just interior designs needed for Broadcasting House and other world wide studios.