Just like the title says, the ICPS and EUS for SLS and Orion have disappeared. Don't know if this is intentional or not. If it is, please bring them back.

It is intentional. Those parts were replaced by the MUS configurable tank; the only thing the older parts have that the MUS does not is integrated engines; I felt it was not worth the part-count savings for the engine alone to keep those two single-use parts around (and their large texture sheets).

No they will not be coming back -- you are free to continue to import and use them from older releases, though they will not be supported.