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Microsoft has yet to reveal how far Windows Phone 7.8 will go to mimic Windows Phone 8 features and UI elements. There are some features that are easy to guess not making jump from NT core used in WP8 to Windows CE used in WP7.X, but things like new lock screen are very much open.
Nokia slide above comes from smartphonefrance that cannot go out and confirm the picture is authentic. That said there’s nothing too revealing here, even the question will WP7.8 get new lock screen is not answered.