As I see it there are two situations.
1: There are no capacitive buttons. This is the ideal situation because a 4.5 inch screen would mean that the bottom bezel could shrink considerably and the overall size would be similar to the 4.3 inch phones out on the market today.
2. There are capacitve buttons and we're looking at a infuse look a like.
As an evo owner I'm okay with situation 1. I'm not okay with situation 2.
This illustration shows what im talking about in situation 1. (from the nexus prime thread)