In the end, two of the three rumored girls are officially part of the new group. Since the information is made official already, no point to keep it a secret anymore, the new members are:
Mikami Yua (M.Y.)
Ichikawa Masami (I.M.)
Just in case anyone is wondering, the third rumored girl was Hoshimi Rika.
The two new members will appear in today's show.
I am not exactly sure why they reveal the information before the show actually airs, which kind of take the surprise out of it. My guess is that they want to reveal the two new girls as early as possible to see if they can boost the sales of their concert tour? Apparently the ticket sale for local concerts on the upcoming tour are not doing too well, which does not come as a surprise since some of the places that they will be performing don't even show the Muscats on TV. Personally, I think it is way too early for them to go on tour since they haven't been around long enough to build a strong enough fan base yet. It took the original Muscats three years before they went on tour and even the original Muscats couldn't sell out a lot of the local venues, let along the new group. I would say based on the new group's first CD sales numbers that they are not at the same level as the original Muscats in terms of popularity. I wish the two new members and the group well though.
Here are a couple of interview with the two new members if you can read Japanese
http://news.mynavi.jp/articles/2016/04/13/ebisu/http://news.walkerplus.com/article/75149/