He is, though. By passing through the anomaly, Worf has already jumped to a different timeline than the one he started in.
Okay, we have a different definition of "Our Worf" here. I wanted to point out that Worf has already entered a parallel universe, not to imply that his personality would have changed somehow; his quantum signature is apparently already out of synch with the universe when he arrives at the Enterprise
Whether his personality has
changed, whether his quantum signature is different from the one of the universe in all the other TNG episodes... We don't exactly know. We think we follow the "same" Worf through all the permutations, but there's lots of confusion there, and in theory "our" Worf could be one of those other yellowshirts who pop up in the shuttle towards the end. Or we could switch tracks and start following an all-new Worf and an all-new universe from this episode on (you know, one who doesn't get surprise parties and does get open expressions of affectation from Deanna Troi). The default assumption is that this is indeed "Our Worf" throughout the entire episode and series, though.