It should happen because this device is less than 18 months old. At last year's I/O, I believe Sammy agreed with Google's proposal that all Android devices should get updates that come out within 18 months of their release date.
The hardware on the S2 can easily take it, so we should get JB. Additionally, JB is more of an improvement on ICS than a wholesale update. So, it shouldn't be as hard to add it.
When, is another story. It should be on our phones by this Fall, but if history fortells the future, it might not be until next year.
That is why I will likely leave Sprint, when my contract is up, and buy an unlocked GSM Nexus branded phone. CDMA's are less prevelant and take longer to update.