After rolling the next Android update, JellyBean a.k.a Android 4.1 on the Galaxy Nexus, Samsung are expected to send it out to its Galaxy S3 in Q4 2012. However the S2 is not believed to be so fortunate – there has been speculation that it will not received Jelly Bean at all. Despite this, XDA developers have cleverly found a way to use Jelly Bean on the S2 (and the S3 which doesn’t have it yet) by playing Dr. Frankenstein and putting bits and pieces together to build a custom ROM.
Samsung Galaxy S2 & S3 Android 4.1 Jelly Bean update via custom ROM
One of these developers, Faryaab, has created and released a Jelly Bean port for the international S3 model. This was originally made for the Nexus but he adapted it for the S3. It isn’t fully functioning just yet with regards to camera, Bluetooth, SD card, Wi-Fi and audio for phone calls; hence the ROM is in alpha stage. For this reason it is inadvisable that you install this onto your S3 so you should probably wait a little longer.
For the Samsung Galaxy S2, something similar has been made by a different XDA developer; LastStandingDroid. This is also riddled with bugs and incomplete so it is up to you whether you’d like to take that risk at the hope of getting the Jelly Bean OS.
If you use your device every day you should avoid these experimental ROMs but once they have been finished fully by developers and the bugs have been cleared up, you could give it a try.