As far as Jack's intent, it's hard to say as he's a fictional character and we don't have his inner monologue explained. I'd guess he was hoping the ship would stay afloat long enough for help to arrive on the scene, or maybe he was thinking about delaying the inevitable submerging to get on a lifeboat.

As far as it went in reality, those who remained on the ship until it went under either would up on the upturned Collapsable B lifeboat, rescued from the water by Lifeboats 4 and 14 or dead. The most notable case is Chief Baker Charles Joughin, who is the last person to have left Titanic and survive. He rose the stern down like an elevator and wound up on Collapsable B after treading water for a considerable time. I'd say this is followed closely by Second Officer Charles Lightoller, who was held against a grate as the bow submerged and escaped thanks to a surge of air from that grate releasing him. He wound up in charge of Collapsable B until the lot rescued by other lifeboats at the break of light. Colonel Archibald Gracie and Marconi Operator Harold Bride are also two notable cases of people who left the ship as she entered her final plunge and survived thanks to Collapsable B.

EDIT:

30 people were rescued from Collapsable B, though it may have started off the night with as many as 60 (hard to know exactly, but there's testimony to a substantial number who drifted off as it progressed).

/EDIT

As far as Lifeboats 4 and 14 went, they plucked about a dozen or so people from the water over the course of the night combined, though not all who were rescued survived exposure. I know at least 2 perished despite efforts to warm them up.

By the time help arrived nearly 2 hours after the ship was gone, unless you were in or on a lifeboat, you were dead. Simple as that.