Tesla fears the Osborne Effect precisely because people will think the Model 3 is almost as good as the S but only costs half as much.
Tesla is in a difficult position because the S is already lacking in creature comforts compared to other cars which cost $70k to $140k. Because of the lack of luxury interior, it will be difficult to differentiate the 3 from the S in many comparable factors which matter. We already know the 3 will have very good range, acceleration, and styling. So these are things it is close to the S on. Tesla's positional challenge is that they have very little they can downgrade from the S to the half-priced 3, because the S is already very spartan in terms of the interior and there isn't a whole lot that can be removed. It's safe to say that removal of the driver's instrument cluster is a pretty ham-handed attempt at finding something, anything, that can be removed to differentiate 3 from S.
It's very, very unclear at this time what effect the 3 will have on S/X sales. If the 3 really is 85-90% as good as the S for half the price, it will dramatically Osborne Effect the S because it will indeed serve as a replacement for the S for all intents and purposes. That being said, if Tesla is busy selling the 3 at a 10:1 ratio to the S, in the end it won't matter because revenue will be so much higher that it will easily offset sales declines in the S/X.