After the whole civil war business is over with, would the Nords try to take any land from Morrowind? the only thing that stopped them before was protection from the Tribunal. Now that is gone, and Morrowind is weakened. Do you think it is likely they will invade?

No reason to, at least for the moment. Even in the Stormcloak victory, Ulfric commits to rebuilding just so they can be ready for the inevitable sequel to the Great War. Not to mention that Blacklight is now one of the strongest cities, rivaling Mournhold from back in the day. The Nords would have a tough time making it through there, and they no longer have the Tongues bolstering their ranks.

What is the source for knowing that Blacklight rivals Mournold? I have not read that yet.

http://www.uesp.net/wiki/Lore:Blacklight Evidently, its also the new capital of Morrowind.

Dragonborn reveals that Blacklight is the capital of Morrowind now.

Also, they won't invade Morrowind unless Ulfric is really that stupid. There are bigger matters at hand with the Thalmor than needless conquest. Plus the Redoran will probably kick their asses if they try. Morrowind may still be in rebuilding mode, but Skyrim is coming off a civil war.

I knew it was the new capital, but I hadn't heard it rivaled Mournhold.

I think that part's dialogue from Morrowind.