But he could return to action for the Ospreys as early as next week, putting him in line for the autumn series for Wales in November.
"Gavin is back in full training and close to a return to action. He is on schedule and we hope to include him in contact work soon," said Ospreys coach Sean Holley.
"We have to see how he reacts but then game-time is the next step for him. He could be ready for the Ulster game."
Henson's recovery is the second boost in a week for Wales after it was confirmed that 2001 and 2005 Lion Martyn Williams will not require an operation on his left ankle.
But Warren Gatland must wait on scrum-half Mike Phillips who met a specialist on Thursday night for an update on his knee reconstruction.
Wales face South Africa on November 8 before clashes with Canada, New Zealand and Australia this autumn.