DP exactly.
But apparently even with the rumoured "geared turbofan" the economics of the E-Jet won't be able to match that of the Dash.
The other question about using it on the longer routes is that what are you going to do with it when it isn't flying the longer routes? It's going to have to fly the shorter routes, and probably alot of them. If you based it in a particular base then you can only use it on the long routes that base has, so how are they to be distributed across the network? I have heard the 175 is still too heavy for GCI too so it'll have to avoid there.
Again as we were told, it is very, very unlikely to happen, but as this is the aviation industry then anything can happen at any time.
CC