Obviously no one can know for certain. There have been numerous examples of athletes who manage to come back to their best after injuries, and many cases of athletes who are never the same once the physical ailments start piling up. Jakob is still relatively young at 24, either scenario is certainly possible.
But what say the gut feelings of the oracles of Letsrun: Will we see Jakob I. back around his best level again? If so, when, at what distances? Or is it the case that we have simply seen the best of him, and he will now be caught in the quagmire of recurrent injuries and setbacks the way his elder brothers have. I must say, I had expectet him to be clearly off his best in this comeback seeing as he has had so little specific training, but the sheer distance he was from his typical form jolted me. Hardly a real contender in the 5000m either in this shape.