Yeah the correct way to interpret "When these roll they are now replaced with..." is that you can still bind with a demon that has it.
But we know blizz... their patch notes and reality is 2 different things.
So at this point, we can only guess.
The downside is that you need 15 hard points in bind demon to be able to do so.
And you also get forced to invest much more points into demonic mastery.
And on top of that, blood oath becomes also more important to max, cuz we already know it's the best defensive skill in the game, but since they also want to nerf the demon's hp, he may need the bonus life% from blood oath to survive.
But this is just speculations too, cuz we don't know how hard they will nerf its life.
In the end, to obtain the same power we currently get from 19 points in the demon tree (1 in each, 20 in blood oath), we will need 62 hard points, which is not feasible cuz all builds need ~63 skill points to max their offensive core skills.
The total skill points needed is not only a nerf for end game builds. It will severely affect the early game.
You'll need to invest all you skill points from lvl 30 to 44 into bind demon to obtain the same thing you normally had at lvl 30.
That's 15 levels later, while all those levels do not improve your core dmg.