leave the wall?

That is a bautiful room. Leave it as is. Assuming your furniture and rug will remain the same, all is too formal for what I think you are going toward.

We are actually dealing with the exact same problem. We have that cool classic plaster molding in our dining room, and when we knock the wall down, we are trying to figure out how to do the transition.

We are looking at having a customer plaster guy come out and do the same kind of plaster work, but it is extremely expensive.

The other thing we are thinking is just buying large molding that looks similar, rip out currrent plaster molding, and redo the entire kitchen and dining room. It is cheaper than custom plaster work and our best option right now.

Have you figured out what you are going to do yet? I am curious to know what you came up with.