Actually, there’s already a PS2 version of Kazoku Keikaku (and in a way, Casual Romance Club), so I don’t think the presence of a port automatically eliminates the chances of localization. I guess it depends on which companies are involved.
What’s a real blockbuster anyway? From a personal perspective, we might suggest highly rated, text-heavy games. However, as far as a business is concerned, it’s about what makes money.
If games like Snow Sakura, Princess Waltz, and Kazoku Keikaku sell well, then I’m sure we’ll see more of these fan requested titles (it’s ultimately conditional, isn’t it? These are more time consuming to localize, so sales had better justify the effort). However, they’re always looking in different directions to find hits. For all we know, Cleavage or Moero might just become the “real blockbuster” for JAST USA, whereas something like Haruka ni Aogi, Uruwashino might be a money loser.