No mentions of the Hellfire Club. But one theory is that these unnamed characters will be them, and not the Shi'ar. Jessica Chastain has stated on Twitter she will not be playing Lilandra, despite her character being called an alien. Maybe Skrull? Maybe Deathbird? Maybe Selene? Maybe Cassandra Nova, even?
Shaw was much, much older in the movies, even older than Xavier or Our Lord Magneto. He was a Nazi scientist during WWII, and he was killed by Magneto and... stuff was done to his body. His death was before the time change, so it should be unaffected. There shouldn't be any more Sebastian Shaw, ever.
Emma's only been seen in Origins: Wolverine, and her only power seems to be her diamond form. She's (Kayla) Silverfox's sister and was captured by Stryker in the old timeline. This was prevented in the new timeline, so she's wide open for future development. General consensus seemed to be poor, so I doubt they will bother.
Well - then they are potentially stepping into dangerous territory. One of the core messages in the Dark Phoenix saga is that power corrupts - but presumably Jean would have been able to handle it (due to her virtuous nature) if Mastermind hadn't stepped in to manipulate her. Without the corruption from an external source, they are essentially saying that a very strong-willed woman can't handle power- and that can be a very explosive topic these days.