That article is silly for several reasons.
For one, it IS the OEMs who aren't upgrading the phones. Google can't make them.
Two, any apps that won't work on your platform won't show up on the market on your device. If you can see it, it will work with your version of Android. If you have an Android 4.0 phone it will show all apps from Android 2.X. If you have an Android 2.X phone and there are apps that only run on 4.0, you just won't be able to see them. This is the same as it has always been.
Three, most Android Honeycomb apps simply resize themselves and adjust the layout to a larger screen size. This way they can adjust to 3.5 inch, 7 inch, or 10 inch screens without having to make different versions. They won't be marked as a tablet app because they're not tablet apps, specifically. Examples of this include Gmail, the Market itself, and the Engadget app. This was done in anticipation of ICS, so that apps work nicely across all device screen sizes and the user doesn't have to worry about it.
Tablet specific apps are almost exclusively apps that either are only available on larger screens (like Google Body) or the developer wants to make more money by selling the tablet version separately (like MLB At Bat or Slingplayer).