Nokia has updated its offline maps on multiple Windows Phone 8 devices as of late yesterday. Offline maps can be used in conjunction with Nokia Drive Beta to allow users to get directions, local POIs, and access to other features where an Internet connection is not available.
So far, several Nokia handsets and the HTC 8X have all been triggered for the update. It is likely that all Windows Phone 8 devices will receive the update, but there has yet to be any confirmation that WP 7.x devices will also get the updated maps.
The update files seem to be an entire replacement for the files currently stored on the phone, rather than a change of data piece-by-piece, as the download size for the entire USA update is the same 2.4GB which were required for the original files to download to my Nokia Lumia 920. Be warned that you must stay on the download page for the update to process, and be aware that larger updates for those with more downloaded maps could take longer than an hour.
Does your WP8 or WP7.x device have an update ready? Go to Settings > swipe to Applications > Maps > Updates to check and let us know.