Not at all. Ethernet is ancient and there are other transport protocols besides TCP that can and have used it in the past Apple Talk, IPX/SPX, DecNet to name a few. This is the beauty of the OSI model. Ethernet at layer 2 is independent of what rides it at layer 4.
OSI is just a model and it is not limited to end stations. What gives you that impression?
Conceptually and virtually switches most certainly do exist in the OSI model.
For all practical purposes a switch can be thought of as a multiport bridge. And as such it exists at Layer 1 and Layer 2.
I didn't say anything about end stations? The point is that a switch is inherently a violation of OSI layering (it uses layer-3 information to make layer-2 decisions), which given that practically all modern networks are switched, suggests that the 7-layer model may not be that useful for modelling real-world networks.