I admit upfront that I prefer the Kate/Sawyer coupling. However, it seems to me that the way that the storyline is heading Kate and Jack's characters are taking completely different paths and it will not be allowing them to make much of a connection in the near future.

I think the tension between them in last nights episode was very realistic. She feels tremendous guilt and disloyalty over leaving Jack behind, coupled with guilt that her feelings for Sawyer are stronger than her feelings for Jack. Maybe she feels she compromised Jacks safety in asking him to save Sawyer.
Sawyer feels hurt by her strong feelings for Jack and her apparent guilt over their relationship. He also is not accustomed to getting so attached to someone, he views it as a weakness. Therefore he will tend to sabotage it, protecting himself.

I do not believe the Sawyer/Kate relationship will ever be a simple boy meets girl and they fall in love and live happily ever after in the love shack of life. Not possible, they have more baggage between them then could have possibly fit on board flight 815. They are connected in a bond of mutual love and affection that I do not see being completely gone.

As for Jack, I think he is going to be heading into a direction that is more central to the show, but not from the romantic standpoint.