Responses

I agree with you that it *would* be progress, and some nice intimacy... but let's be honest, no way are they going to just sleep. It'll be the same thing as usual: "You said you wouldn't do anything!" "I know senpai, I just..." "Damn it!!! I can't trust you at all" Morinaga ignores him saying "Stop" because tsundere yaoi logic etc.
OR Morinaga does just cuddle him but then senpai starts fidgeting and more "Damn it, this is all your fault you're always like this" and tsunderes them into doing it. Same old same old.
I think sleeping (and just sleeping) together is actually a pretty big step forward. It's closeness that isn't sex or passed-out-after-sex, and that's meaningful. Senpai is getting accustomed to Morinaga physically, whether he realizes it yet or not. Of course, I enjoy seeing them do more as well /wink.
I really want to see him waking up tangled together with Morinaga :)