Sadly, unless we get to put the meta AND sha-touched gem into this weapon, I don't see the point of even having them in the game at this point. There's no build-up to the legendary, it's just "do irrelevant quest A, do irrelevant quest B, then get legendary on quest C", whereas with Shadowmourne, Dragonwrath, and Fangs of the Father, they all had build-up. You'd start by crafting the first weapon, (especially with Shadowmourne), then you had to upgrade it to its next form (with Shadow's Edge, collecting souls to make it Shadowmourne), then you had to upgrade it one last time using an item from the final boss of that tier to turn it into the legendary.
With this though, you get a gem that only works on T14, then a prismatic socket that also works for T15, but we don't know if it'll work for T16. We get a Meta gem in T15 along with a socket that we don't know where it will go, but this meta gem replaces our current one. Who knows what stupid shit we'll get in T16?