Any plans for neutral or civilian traffic?
 

One of the challenging things I enjoy about Dangerous Waters is the presence of non-enemy contacts and the need to classify contacts correctly before opening fire.

I haven't seen any civilian or neutral (or even friendly) surface units in the game and I'm wondering if there are plans to introduce any? Would make for a greater challenge than blasting away at every contact sure that its enemy.

I'd hope for friendly contacts at some stage but I wonder how much civilian traffic there'd be in the North Sea if the Cold War suddenly went hot. I'm guessing not much.

Depends on air cover and proximity to hostile forces. Some countries rather depend on it. Shipping going to and from the UK would be one to keep.

At the time, Ghent Belgium was a port used by the U.S. military. I would suspect that French ports would take logistical ships, too.

Realistically, I don't think you will see much neutral/allied traffic in most of the operation area. Merchant would get out or seek safe harbour within 24 hours of the war and allied surface group will stay well within land based air cover range. Norwegian, Danish, German, Finnish surface unit will probably stay within the Baltic sea and coastal waters.

Now, if we get other theater of operation, I'm sure we'll see more neutral/allied traffic.

The only civilian traffic I'm willing to accept is if they're part of a convoy you're tasked to escort (if such missions would be implemented).

As for allied forces, that could be interesting.
In a big conflict like that cooperation between various allied countries might not go as smoothly as expected and you could from time to time stumble upon subs from other countries - sometimes on their own, sometimes as a "3rd party" during missions.
And here are also the possibilities of escort missions.

But I think we'll get NATO forces eventually... probably along with a Soviet campaign.

Sub generally do not do escort mission. Even the ones for CVBG is not really in formation. They're usually well ahead clearing the path.