I rewatched the scene, and that wasn't my take at all. On the other hand, Michelle Matland's main style inspirations for S2 for Shiv were Katharine Hepburn and Marlene Dietrich, so maybe the costume folks were trying to tell us something. Shiv realizes that she's a lesbian: possible arc for S3?
...In all seriousness, I'm not sure if we were supposed to interpret Tom and Shiv's beach scene as a final breakup, but Jesse Armstrong seemed to imply that it was: "In regard to the show, it's about that delicate moment of which you say 'That's too much. I can't do this anymore.'" If it is a final breakup, it would make Shiv's subsequent decision to beg Logan to spare Tom that much more poignant. Not only would it mean that despite the horrible way she has treated him, she does in fact love him, and that she loves him enough to sacrifice her career aspirations to protect him (as Logan unkindly made it clear that making Tom-type sacrifices was the stuff CEOs were made of), but that she loves him enough to do it even when she can't possibly benefit from it since Tom has made it clear that he's done with her. That's quite beautifully tragic. Shiv finally proves her love when it's too late for it to matter.
The real Shiv (Elisabeth Murdoch) was married several times (to men), so it seems quite possible that we're going to get a divorce storyline in S3, although I don't know how Matthew Macfadyen could stay on the show if there's no reason to keep Tom in the Roys' orbit. Shiv could even get a new man (or woman). Elisabeth's second husband was a PR executive, and the writers could have all kinds of fun with that.
And speaking of tragic, it's sad that for all S2 flirted with interesting stories about women and power, Shiv was ultimately forced to make the same bullshit choice women have always been forced to make in the working world: choosing between her career and her man.