Please please please do not rework Nocturne's ult.

A global dash with zero counterplay. Lol

I agree, but I don't think that he should be able to cast abilities while traveling, there really isn't much you can do when his Q and E is on you before his ult even gets to you

They're not touching nocturne this was confirmed awhile ago.

Even if they choose to work on Nocturne (which they have already said they won't in the assassin update), there is virtually no chance that they will rework his ultimate. They've said before that they like it, and they've never shown any kind of distaste for semi-global mobility on long cooldowns. I would not worry.

I doubt Riot would rework Nocturne's ult outside of "make everything dark, then jump onto a target". They might throw one or two extra things onto it, but as you said it's core to Noc's identity as a champion, and it doesn't take a Nocturne main to understand that.

They announced they won't rework him, as he is more of an all-in fighter than an assasin.

It should only effect thd target he's dashing to.