Wuk doesn't join the scions
There is a voiced post credits scene where the WoL recieves a letter setting up .4 and .5 and the game makes your WoL willingly decide to allow Wuk to accompany them, there is no option to even allow you add your own opinion to this event

You thought you could put me aside when the MSQ ends with 7.3? Hahaha im gonna stay in FFXIV forever as the Main Character

IM GONNA STAY WITH US FOREVER AND DONT FORGET IM THE MAIN CHARACTER NOW