I'm booked on the Sea Princess for 2005! Southampton to New York, via Ireland, Faroe Isl., Iceland, Greenland, St. John's, 14 days, Sept. 10-24th.
All the major cruise lines do some sort of Transatlantic/Repositioning cruises in the Fall. Some have a few ports, and maybe 5 or 6 sea days, they range in length from 10 to 15 days.
Cunard still has the England to New York that is strictly Transatlantic, no ports. Weather in Sept./Oct. can be a factor no way to control it. Could be great or ugly or a little of both!
Carnival even has a crossing in October next year from Rome to Florida, I think it is a cruise mates group cruise.
Check all the major lines, Sept./Oct./Nov. schedules or Spring (April May) when they take the ships over for the Med./Europe season. Spring weather is a little more predictable than Sept./Oct.!