It has now been confirmed that Tomb Raider: Definitive Edition will not be coming out for the PC.
A recent FAQ section was posted on the Eidos forums that confirmed that Tomb Raider: Definitive Edition is only going to be available for the PS4 and Xbox One.
Tomb Raider Definitive Edition was designed and rebuilt from the ground up for next-generation consoles. At this time a PC update is not planned.
It has also been confirmed that there will be no “upgrade program” available for those that already own Tomb Raider on PS3 and Xbox 360. If you want to buy Tomb Raider: Definitive Edition, you’ll have to pay $59.99.