So when Varian Wrynn died he dropped his sword Shalamayne, which is a weapon on the same level as Artifact weapons. Due to the proximity to the Tomb of Sargeras it would be impossible to reacquire at this time but I have a feeling it will play a role later in the expansion in something I feel has been a long time coming.
Anduin will become a Paladin.
There are a lot of factors regarding this change that make it plausible.
1. Anduin is the son of a Warrior, and a good one at that. He's also named after Anduin Lothar, a legendary Warrior, and Llane Wrynn, another Warrior. He comes from a legacy of Human Warriors and there are even scenes from the comics of him sparring with his father using a sword and shield. The origins of Human Paladins are simply Warriors infused with the Light, which means he's just an armor change away from making it a reality.
2. In the Paladin Order Hall you acquire a Nelf Paladin follower, which normally would be impossible. Delas Moonfang is actually a priestess of Elune who converts from Priest to Paladin after you fight Balnazzar in the campaign. There is a ceremony for the change and everything. It's clearly possible, and within the Highlord's power to do so.
3. Shalamayne is his legacy. If the sword is recovered it will no doubt be returned to him, and no Priest wields a sword. It will be the final piece of the puzzle.
4. With Turalyon returning to Azeroth (possibly) Anduin would have a Paladin rolemodel to show him the way on his new path. He was mentored by Velen, which would explain why he pursued the path of the Priest.
Even if it doesn't mean change for Anduin that sword is a very important relic of the expac's greatest hero and it would be in Azeroth's best interest to recover it.