T-Mobile just announced via Twitter that its iteration of the Galaxy S II will be getting the Android 4.0 bump come June 11th.
Samsung Galaxy S II owners: @Android Ice Cream Sandwich is coming via Samsung Kies starting 6/11! More details soon!
— T-Mobile USA (@TMobile) June 1, 2012
No update doc is yet available on T-Mobile's website illustrating the changes, but one should be coming sooner rather than later. The update will take place via Kies.