I like this idea a lot. The obvious counterargument is “Why not just use the local graph”? I think the answer is that we spend much more time in the text view than graph. Moreover, you could effectively get a 2 Depth local graph while only showing 1 depth, since hovering the link takes care of the first step. By seeing all the notes that the linked note links to, it might give you more context about what it contains than a text preview.
Stil, the text preview is quite useful. So, perhaps a different hotkey can be used for Graph vs Note preview - Ctrl and Alt?