The second U.S. operator to launch Samsung’s Galaxy S II last year appears to be the first that will upgrade the smartphone to Android 4.0. T-Mobile tweeted the information on Friday, saying the software update for the Ice Cream Sandwich version of Android will become available on June 11.

Users will have to download the Android firmware through Samsung’s Kies application, which is supported on both Windows and OS X. This differs from most Android software updates, which are generally pushed out over Wi-Fi or mobile broadband. Given that this update isn’t a small bit of code — it’s full firmware with the new operating system — the file size is likely several hundred megabytes in size and therefore easier to transfer via a USB cable.

T-Mobile will offer additional details on the upgrade soon, although I’m fairly certain of one detail: Most Galaxy S II owners won’t see much visual difference after the update. Based on the experience with Android 4.0 for the Galaxy Note, which was upgraded earlier this year, Samsung’s TouchWiz user interface will cover most of the Ice Cream Sandwich UI improvements. However, the many new Android 4.0 features will be welcome by Samsung Galaxy S II owners: Monthly data usage monitoring, an improved camera interface and widgets that are re-sizable and more interactive, to name a few.

News of the update follows a Samsung announcement from earlier in the day: The company has sold 50 million of its Galaxy S and S II handsets to date, with the Galaxy S II accounting for 28 million of those sales.

Related research and analysis from GigaOM Pro:
Subscriber content. Sign up for a free trial.

• The future of mobile: a segment analysis by GigaOM Pro
• CES 2012: a recap and analysis
• Carrier IQ and the continued erosion of operator trust