Several artists have gone for 7 singles or even more after selling millions of albums. The best example is Michael Jackson's Bad, which had a flop for a 6th single but rebounded with "Smooth Criminal" for a 7th single. Jackson's Dangerous produced 8 Top 40 songs. Shania Twain's The Woman In Me and the Dixie Chicks' Fly also produced 8 hits. Of course, Twain's Come On Over produced 11-12, and could've gone to 13
Swift's already said she's taking a long break, so the public will be ready for her when she returns. With no new album coming up right away, she should go for up to nine singles (her fans said she has two possible hits left after "New Romantics").