Their musical style probably wouldn't change much... There's no point in going if they would sound like every other Morning Musume/AKB48/etc. group in Japan, they already have enough of those.. how many groups/subgroups are there within Morning Musume and AKB48 alone?
If anything, I'd hope they would release one or two older songs as their first singles (Bo Peep Bo Peep) since they were already tested and proven to be successful in the market. I know a lot of people complain when other groups do that, but their expansions to Japan aren't necessarily to please existing fans, but to gain more fans in that country. I also need a real HD version of the Bo Peep MV now that CCM finally upgraded their cameras.