You know why (IMO) we're seeing such a diverse mid-lane at worlds?

The AP Itemization changes.

Those changes blew the door wide open and helped the viability of alternative builds while keeping what we considered standard builds relevant. All these price and item changes made things like Tear -> AA Scepter more viable because it now gave far more AP. The amount of late game items went up while still offering raw damage vs. utility picks.

By contrast, compare the AP Itemization to the bruiser itemization. Rather than open up and allow for more diverse paths such as Deadman's + Sunfire being on equal terms or having tank itemization being super amazing, most of this itemization made the new items completely overshadow old items. Deadmans/Black Cleaver is pretty much core on any AD bruiser. Sunfire has almost been erased from existence. Even the NEW items such as titanic hydra and steraks are seeing only occasional play in favor of the old items of Randuins, Spirit Visage and Banshees.

If the Marksmen itemization change is like the AP itemization change, we're going to see bot lane cracked wide open with the amount of "viable" characters we can have at any time. If it's like the bruiser/tank changes, I think we're just going to see the same picks with fancy new toys as we always have.