We haven't had another reference to it, and it is a bit late for it to be pre-realisation, so maybe it will turn out to have just been for that scene... although I suppose they could have done the shopping/ordering off-screen.
Well in terms of time passing within the story, the bed conversation likely didn't happen that long ago. It happens at the end of chapter 10 and then chapter 11 is the wedding. Its true that a lot of chapters of flashback (the dark days) happened in between putting physical page distance between it and the current point, however I don't think it would be odd to see this plot point again since its possible it might have happened just days ago.
It could be pretty fun... Ayako gets home from work to find Asuka unusually exuberant... "Hey mom, guess what happened today"... throws open her bedroom door, throws herself on the bed and poses "***our*** bed arrived!" (big grin).
I suppose there could also be a call back much later, going bed shopping as a sign Ayako has completely accepted their relationship (along with some "I can't believe I was that oblivious" reminiscing).
I hope we see it again since you're right. It could be pretty fun to watch the possible scenarios play out. Also if it gets brought up again it puts pressure on the two of them to share a bed together again. I also don't see Asuka just forgetting the fact that she used to be able to sleep next to Ayako every night and then was told she couldn't until they get a new bed. Shes definitely going to want that bed if she can get it!
(mood reasoning: With confirmation Ayako feels the same way as she does (even if they aren't supposed to be acting on it), Asuka is going to be on cloud nine for a while... I wonder what Rui will make of it)
I think Jun at least is certainly going to be suspicious since he knows Asuka is in love with Ayako and knows there are probably only a few things that would make her this happy. I wonder if Asuka will tell him herself since he seems to be more or less accepting of her situation even if he doesn't think its normal and I imagine Asuka might want to have someone to talk with someone about it depending on how things develop. Although I suppose Akira could also work, but I can see Asuka being a bit hesitant to go to her.
As for Rui, I can see her making a playful guess that it has to do with her mother, and Asuka being unable to hide her emotions could lead to Rui asking more questions about what could possibly have happened with her mother to make her so happy.