I've had a generic 'welcome to Rails of Sheffield, former Hattons customer' email, that was sent on 18 March 2024. I haven't had anything specific about the Genesis coaches yet, but IIRC the original delivery date for these was May/June time? It's perhaps a bit early to be worrying about something that probably hasn't arrived from China yet.
As you say, integrating an entire customer database into their system is going to take time, and we don't know where Rails have got to in that process. Don't forget this is something they have taken over in addition to their existing business, so it's not going to happen immediately. Once Rails have a confirmed delivery date, that's when they will probably start sending the emails out, and we can ask questions from that point. (I'm sure it will be announced on RMWeb). Until then, no news is good news as far as I'm concerned.