After how the 2.3 story ended (I aren't going to spoil it for people who might not be there yet) I can see 2.4 being the introduction of the Ishgard storyline, and Shiva will be linked to that. 2.5 will carry on the Ishgard storyline and after that I can see the first expansion coming, ending the Ishgard storyline, and finally opening the city to PCs.