Yes, eventually we will allow for that. It's on the backlog list. In the mean time, are you aware that you can forward emails into your GTDNext inbox? Just email Inbox@GTDnext.com from the account you sign-in with.
I realize this isn't a substitute for links in notes (or in task subject lines) but it does at least allow you at least to get the whole email into your notes, so you can refer to it easily.