There have been rumors and official statements. No exact release dates have been offered so far for the udpate to Android 4.1 Jelly Bean for makers of models other than the Nexus series. See Android 4.1 Jelly Bean features.
HTC issued a statement regarding the HTC One S/X/XLS stating , "At this point in time, we can confirm that we have plans to upgrade our HTC One X, HTC One XL and HTC One S to Jelly Bean.
SamMobile reported that Samsung is almost ready to update the Samsung Galaxy S3 (III) to Android 4.1 Jelly Bean as early as August or September. It was also reported that the Samsung Galaxy S II will be updated to the new operating system.
Before updating any smartphone is always a good idea to backup all of your data. We also recommend that you read what the update does, it sometimes changes the homescreens and settings such as taking a screenshot which can be confusing. Sometimes updates ad glitches while fixing others.
The most recent example of minor glitches in an update is the Samsung Galaxy S II Skyrocket to Android 4.04 ICS, our readers have complained of glitches but do is drive them crazy.
The unlocked international version of the Samsung Galaxy Nexus and Nexus S are updated to Android 4.1 Jelly Bean. The updates are also cutting out some features due to the massive amount of patent infringement lawsuits between all the smart phone makers. For example the unified search feature was squelched in a security update for the Samsung Galaxy S III to avoid lawsuits and bans of the next big thing.