If the PC port were to have exclusive features they should only be visuals, special effects, FPS and performance. Gameplay should remain the same in all platforms.
You mentioned gameplay, so I'm interpreting that as the combat system only.
Would you include the story scenario too?
Thinking closely on it, I can see why people would be peeved to be missing out if they didn't own a powerful enough PC to experience the game if it is entirely built from the ground up with new scenarios and gameplay as hinted at in the article (if this will actually happen at all is another thing).
I can see people not appreciating having paid for the day one edition, only to realise later on that there's a better version so they'll need to buy again.
Even so, I think sales would be quite high if they did do what the article suggested. People would be angry yes, but the sales would still be quite strong.
I dunno... I might be weird here but I'm ok with buying games again, but only if I deem them worthwhile if course.
I own multiple copies of Ocarina of Time. N64, Gamecube (x2 since one came with the Zelda collectors edition, which had majoras mask, and the one that came with Wind Waker), and the 3ds version.
It's probably not a popular opinion here but another way to look at it is, I think a game being completely different on another platform would be enough reason to buy the game again to experience the new stuff, especially if I enjoyed it immensely the first time around.
Edit: just though up of a scenario in which I had to buy a game twice to experience new additions. GTA4: Episodes of Liberty City and the original base GTA4.
Granted I didn't find it that enjoyable but I was willing to buy it again just to play the two episodes - which were great.
