HTC’s Updates on Android 4.1 (Jelly Bean) and Frequently Asked Questions page made it clear that devices having RAM 512MB or less will not be upgraded to Android 4.1.
That means there are several devices which won’t get this upgrade and at present it includes HTC One V and HTC Desire C. These two devices will remain on Ice Cream Sandwich as both phones have just 512MB of RAM.
The smartphones released in the year 2011 will be considered for Android 4.1 updates after the Jelly Bean development on devices released within 2012 are completed. HTC confirms that upgrade to Android 4.1 will include the latest Sense 4+.
They are planning to make generic development ROMs of Jelly Bean available for both the HTC One X and HTC One S for the developer community.