No, they'll still be there, and certificates issued by them will still be valid for their normal duration. (Like if a certificate is issued today by R3, then it will still be valid for its usual three months from now).
They haven't given an exact timeline; the closest is this post saying that it will likely be in the afternoon (North America time). I think they have a lot of things to line up to get it done and don't want to be tied to some external timetable.
For RSA certificates, yes. ECDSA certificates (which newer systems often use by default) will be issued from E5 & E6 initially.