The phrase "new subtitle" refers to a fresh or recently added title or caption that is used to give additional information or clarify something in a book, movie, or other form of media. Full definition
He has created fresh new subtitles for the early New Wave masterworks of Jean - Luc Godard, including Breathless, and worked with Godard personally on the director's most recent films. (rialtopictures.com)
The first trailer for Sledgehammer Games» instalment of Activision's yearly cash cow is in, and it bestows a sparkly new subtitle on this year's game, as well as giving us a look at what Advanced Warfare actually means. (dealspwn.com)
In the blog post, they refer to this as the «Shouldhavebeenedition» (which I also think would've made an awesome new subtitle!). (indiehangover.com)