Q:So, I got this knowledge for possible information on the next two sets from the back of the book "Test of Metal", which is supposed to be explaining what happened to Tezzeret since Jace last ripped his mind apart and Nicol Bolas revived him, granted, without his etherium arm. [In case you don't read the books, that's just some part of the current canon storyline. Long story, haha.]
Anyways, this information is supposed to be a summary to hook you into the next book, "The Quest for Karn". Here's the snippet, word for word:

"Venser--former apprentice and friend of Karn, Mirrodin's creator--and his Planeswalker allies Elspeth Tirel and the geomancer Koth know of the Phyrexian contagion and search for a way to contain it.

The potential savior and destroyer of the plane, Karn fights the corruption building inside him. As the new Father of Machines, what could stop karn from spreading Phyrexia throughout the Multiverse? Even Tezzeret, armed with the secret of etherium, recognizes the consequences of such an outcome. If he can't master Phyrexia, he will look to those who can.

The corrosion begins...

MARCH 2011"

From that, I gather Karn will be printed, but I'm not sure if he'll be a Planeswalker. If I remember correctly, he lost Mirari, which was his way of planeswalking in the first place. I'm not sure if he'll be evil or good, but it sounds like he'll probably bear the Phyrexian symbol [if not a 'walker], even if his intentions are good. Tezzeret is guaranteed to be dipping into black mana to try and control the Phyrexians or whatever. I'm not sure if he's doing it for evil, but rather trying to save his own hide from them and be able to protect himself better. From the book "Test of Metal" [at least as far as I've read, which is almost the entire thing], he seems to have changed personality when he was reborn. I'm not sure what his plan is yet. Should be an interesting ride I'm guessing!