If they play around this, you can just cycle this or something else instead of casting it. People will try this, and whether it is good will depend on what's around and against it.
I'm hoping D can serve as any color of mana for devoid cards. That would be really neat.
Also, the symbol should be abbreviated as "D" and not "<>", the former is shorter and D stands for "devoid".
If anything, we should call it "C", for colorless. Which will most likely be the way Wizards will abbreviate it, considering that they recently freed up "C" (see here, under 107.12).
My arguments for D:
"C" stands for "color," so the letter after C should stand for "colorless."
D also stands for "devoid" and "diamond."
The shape of the capital D is topologically equivalent to the new diamond symbol.
D is the fourth letter of the alphabet, and the new mana symbol already has four sides.
I will put my hat into the "Diamond as Colorless Mana, Numbers as Generic Mana Costs" re-templating ring; but, I'm rooting against <> being the way to type "one colorless mana." Personally, I think a capital letter, such as D, would suffice. The cards, if fake, are really good ones.
My arguments for D: