So people are pretty certain this is gonna be a thing:
We can discuss the many reasons why this leak is probably legit (the argument for it is mostly predicated on the art, but the mechanics and change in templating have precedence in the Great Designer Search and some complaints Maro made on his blog about the dual meaning of the ① symbol), but the larger interest as it pertains to this topic is how these cards look like they could be adding an axis of adjustment to the power of the basic land.
First of all, so that we're clear: The ♦ symbol seems pretty obviously to indicate
specifically colorless mana. This is as opposed to ①, which, as a cost, can be paid with
any color mana. The idea is that colorless, having picked up a little bit of an identity of its own in the past twenty years, is getting broken out into a little more of a sixth pseudo-color.
So, consider this: Wastes lacks a subtype. All the other basic lands are "Basic Land - Forest" or whatever, and Wastes is just "Basic Land." This plays to some of the misgivings they've
previously articulated about breaking cards that assumed only 5 basic land types, but it would work if they incorporated a new rule that Basic Lands, in addition to whatever else they have going on (or, more probably, but of less interest to the topic if true, only if they DON'T have anything else going on) can tap to make colorless mana: ♦.
If ♦ turns out to be a thing that people would ever actually want, then the mechanic plays out like the idea some of you had on the table earlier, where dual lands would be the elementary balancing point for what a basic land could do. Only thing is is that the dual nature would always be split between ♦ and a color. Other dual lands, like the Alpha originals and shocks, which have land subtypes and thus get to tap for two colors, would nonetheless be prevented from tapping for ♦ by virtue of the fact that they lack the Basic supertype.
Ramifications and context:
-In Elder Dragon Highlander, you can only have cards in your deck that match the color identity of your commander. For colorless commanders, that means you don't get a basic land. Printing Wastes solves that.
-Pretty much every format right now (eternal as well as the current standard) has a very easy mana base and there are a lot of people who wanna see more reward in sticking to a deck with fewer than three real colors. By adding a sixth pseudo-color that the more modest decks have an easier time getting into, you can achieve that.
-When the Khans sets rotate, they'll be taking fetchlands and tricolor taps with them. What dual lands are gonna be left?
Well, you've got these guys, which tap for colorless and punish you if you arrogantly trying to use them for anything else. Them, plus the thirteen other lands that tap for colorless, give cards with a ♦ cost a cushy place to land their debut.
-Return to Zendikar is the first two-set block (although Khans was definitely designed for the transition). One of the reasons they wanted to go to a two-set format was that they felt like they didn't have any license to do anything cool with the small sets in every block since they wouldn't have enough room to fully realize their design; moving to a medium-sized second set was a way to consolidate their space. What better way to initiate the new publishing format than to take full advantage and launch a new evergreen mechanic with its own symbology and everything?
