Problem
Region names from theme .info files have been translatable forever. Localize.drupal.org extracted them for good, translators translated so localized admin interfaces could say "First sidebar" or "Footer" in the admin's language. With the layout module defined static layouts, this is not possible anymore. The layout label and the region name are both only check_plain()-ed for output (in layout_page_view() and layout_page_list() respectively).
Proposal
We should figure out how to localize these. Should the plugin t() them when providing the definition or should layout module assume it would need to t() them. t()-ing in layout module could be an issue for any dynamic layouts, which are possibly defined in config or other parts of code. Those might be created in a non-English language and translated via the config system for example. So ideally the plugin would return localised name and region labels.