First off im going to say that I believe Archimonde will be alive because we find out that we did kill him, but only the AU version which means there are now 2 of everything.
What this means is theres a second Azeroth permanently tied to our universe and us to them as well as all the other planets out there. There was not a orc invasion on the AU Azeroth though which means they have a lot of manpower for reinforcements but it also means they wont have experience nor the creation of orders such as the Paladins . The paladins were formed during either the 1st or 2nd war with the horde.
What if some event leads us to realize this and we make a pact with AU Azeroth if they help us, they we will help them since their entire timeline has now changed and they will face different threats than we did now and without the orc invasion, they wont have the seasoned troops to overcome future wars/conflicts.
Keep in mind this is fiction/an idea of mine.
I would like to see some of the old cities rebuilt and having AU people to do it would make sense. Also, on the horde side, they could receive reinforcements and rebuild/strengthen horde strongholds throughout the world as well.
An example of us training them would be the paladins. when they were 1st created they did not have much to go by. They pretty much had to be self taught. With the array of things learned over the coarse of wow, you would have figures like Uther, Tirion, Turylion and others at a high potential early and they could help learn more. This applies to the other classes as well