Being that the three new jobs are in Ishgard, and in order to get to Ishgard you have to beat the story up to 2.55, yes you will not be getting the new jobs till you have atleast one job at level 50 already. As well 30 is a good point, giving you many skills to start out with as well as giving you a reason to keeping doing some of the older content (just using the low level rol will insure players new and old are still playing pre-30 dungeons together).