Beta Labs people updated their Ovi Maps 3.06 page by last night to reflect one more minor update to Ovi Maps. Its just two weeks back, when there are the last update to bring a few visible changes and though no change log available for this particular update, it is supposed to bring stability and bug fixes, including fix for "Update" feature not appearing for some users
At least for my region update was not available via software updater. May be some issue. You can download the same via the beta labs directly via this link
Thanks to @mobileyog for bringing this in my notice
There are still some known issues pending
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This feature is only currently available in portrait mode
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Please note that phones without WiFi (e.g. Nokia 5230) will not work.
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Ensure that you have a memory card (e.g. Nokia 5800) or mass memory in your phone
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If you haven’t done so already, ensure you WiFi access point is already in your "Internet" destination folder. If not, please add this via Menu > Settings >Connectivity > Settings > Destination (this may differ on other phones)
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If WiFi is disconnected during download, the map data will not resume and needs to be started again
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"Map Download failed!": Due to changes on the Map data server, you will need to manually delete the following files in order to use the "Update" on your phone. Please delete the following files (e.g. via File Manager on your phone) from your Cities folder (usually on your mass memory E: Drive on your phone).
\cities\maploader\catalog-00.02.41.123.xml & \cities\maploader\cityindex-00.02.41.123.xml
Nitish Kumar's Blog 
normally betalabs software doesn’t appear in SW Updater as it is Beta,not final version.
Oh! thanks for letting me know. I thought it’s changed since Application updates started appearing in.