The updated mediawiki icons have been completed for some time. For consistency and ease of use buttons that refer to the same or nearly identical features should use the same icon assets.
This currently covers updating the VisualEditor icons to the most up-to-date versions as well as using the same assets in the wikitext editor, if these should be separate tasks we can break them up and create dependencies.
note: this was discussed verbally over a month ago, but verbal tasks are easily forgotten when prioritization comes around, so logging it here.