We have seen Nokia Lumia 610 with Tango update previously. But, if this fact is true, then Lumia 610 could be updated to Windows Phone 7.8 update as well now (1066.0.8779.12221).
The numbers, 8773, 8779, seen in the image stands for the WP 7 operating system’s core versions that runs on the device. Seems like Lumia 610 could be upgraded to WP 7.8 update.
If this is to be believed, then this could very well increase the sales of the device, as WP 7.8 looks quite similar to WP 8 update in terms of appearance, along with those additional features mentioned by Nokia that comes with WP 7.8 update.