K, this was me when I woke up yesterday and saw the news of this...

Now that some time has passed, I can throw in a few cents. Firstly, in Eri's case, we all need to to remember as much as it sucks that this has to happen, it's her well-being that must take priority. Her skin condition hasn't exactly been a secret, as it's been talked about (at least online), off an on by many different fans in different places. Hell, I remember members talking about it in JPH!P's very own chat room in the past. Of course, most of us at the time figured that it was just "a mild rash" or a mild case eczema, for sure no one ever thought that it could possibly get this serious. Fact though, it has, and if a substantial break is what Eri needs to properly deal with this, then that's what she needs.
We all obviously wish for her to fully recover and hopefully, some day, return to the entertainment biz. Even with all her experience as a singer, Eri still has (at least IMO) a lot of potential to become an awesome entertainer overall (or at the very least, a hilariously cute "aho").
Now as for JunLin, for me personally it's pretty hard to see either of them go, let alone both of them at the same time. As I mentioned in posts I made in their respective GOTW threads, I was drawn to both rather quickly soon after they joined the group and they quickly became two of my favourite members, not just of the current lineup, but of all time. However, as has been mentioned here in this thread earlier:
since when they joined it was said that it was temporary.
Since the beginning they've been called "Exchange students" which always gave me a sense that they'd be sent back sooner rather than later.
I still remember the episode of H!M where Tsunku (via VTR), told JunLin that they were going to be joining MM. Junjun was still largely relying on a translator, so she had this cute, clueless look on her face, while Linlin started giggling in disbelief and (I believe) just said
"majidesuka"/really? I also remember the subs for that ep specifically translated part of what Tsunku said as "joining as exchange students." Like Slack said, referring to them in that manner definitely gave the impression that even though they were now in the group, that it wouldn't be permanent. Now granted, we all know that that's how it is when you're in MM. The members, and we fans all know that their time within the group is bound to be limited and that one day they would be leaving it. However, this was the first time where that fact was emphasized that strongly right at the beginning when a new member was JUST joining the group.
Now, the pragmatist within me thinks that in all likelihood, their graduating from the group is simply because their working visas (or whatever it is that you call the Japanese equivalent) have likely expired/are going to expire. Remember as well that a little while after JunLin joined MM, UFA made the announcement for their H!P Taiwan branch (if you can call it that), they had the auditions for and formed Ice Cream Musume and Ojousama/Da Xiao Jie. Who knows? It could be that JunLin's tenure in Japan with MM was, at least in part, to help train them to eventually join (possibly even taking a major/substantial role in) H!P Taiwan.
One can hope.