Being able to cook and engage everyone present makes the open concept floor plans a success. 

NOTHING in real estate is ever gone forever..... trends change but they'll return.... 

Much like life itself, home design continues to evolve.  Maybe John Henry, Florida Architect could ponder this question...

I'd say that's true for NEW construction (except for certain price points as you said) Peter Mohylsky .

Forever? No. And both are still common in our area as our market is by far still a resale market.

At least for right now, in the smaller new homes, the trend seems to be for an open kitchen, dining and living area. You will still see separate dining and living rooms in the larger homes depending on the builder.

Our dining room is not used very much. I would prefer to have an open floor plan in our next home.

What's a formal kitchen? I think that the formal dining room & living room might be 'endangered' but that's about it.

Personally, I hate the open concept. Kitchens should not be open to formal areas and I hate people milling around me when I'm working in the kitchen. And I love my formal dining room. I've gotten used to living without a formal living room, but not giving up my dining room. Overall, I don't think one can generalize... I work with clients who don't care about formal rooms and with clients who won't buy a home without a formal dining room, at the least.

Styles and trends come and go. Right now open great rooms are more popular.  Whether or not that style continues remains to be seen.

They had a good run. Now, we shift into practicality & function

Seems like most kitchens are designed to be open entertainment areas. Many builders have just been putting smaller living rooms which can be used as offices, library, or main level guest rooms.

The open concept is the rage in new downtown Chicago condominiums. Decorate how you like, formal or casual!

The open concept is conducive to how people live today. Formal dining rooms.  Older homes that have them are purchased and remodeled to remove them.  Did anyone ever use a formal living room? I thought those were showcases 

On resales, Colonials tend to have a Family Room off the Kitchen & a Formal Dining Room. It's only on these quirky Capes that I see a room or 2 missing. I want all the rooms that traditionally come with a house so I have a Colonial. Any less and I'd feel like I am being cheated. Where do I host Christmas' & Birthdays without a Dining Room? 

Styles come and go about every 30 to 40 years.  Everything mid century is now in style. Wait a few years and people will be sick of open spaces.

Different strokes for different folks.  When my husband was alive I liked having the formal dining room because we usually had lots of guests for holidays and a few other occasions.  Now, I am almost always the guest at family or friends.  So, I turned my dining room into a parlor where I read or sit to visit with guests.

I have an informal dining area in my kitchen which is totally adequate for me and one or two guests. 

Peter,

It really depends on the marketplace.  True for some areas, and not for others. A

New homes around here feature Great Rooms: kitchen and family room combinations. Everyone can be engaged instead of rooms that were divided by walls in the past. Living rooms have disappeared at some price levels or shrunk since families spend little time in a formal living room and the extra space is wasted. Affordability is an issue. Affordability also leads to deletion of formal dining rooms in new construction of smaller homes.

Hope so, I hate closed up spaces.  

No, not gone forever.  Probably will come back in 20-30 years.  Just like the open concept went away and came back.

Less about price points and more about stages of life.

The Great Room for all took over.

Some people like open kitchen, some don't. 

And it is great to have a formal dining area, when it is possible.

Many people still have people in their home if only for large Family gatherings.

My clients typically still prefer two eating areas and then a single large living area. Having two living areas often means one is a living area and the second a man cave or quilting room.

I’ve also seen many formal living rooms become home offices.

Every single 'older' style home with formal living and dining seem to be compartmentalized here in our area and buyers hate them! They want the nice, open plan, easy for living and for entertaining. 

For me, I love my open floorplan but, against my hubby's preferences, I had the architect add a formal dining room - I can't live without it!

When I sell my home, I will probably stage the dining room as a large office, which is what most buyers want these days (instead of the formal dining room)!

I guess, it depends of the size of living. 

Formal living room is out for the moment. Formal dining rooms are out in some price points but, not all. I like my dining room. My formal living room is now my office. Dog bathing areas seem to be a new trend. Large showers and no soaking tubs is also a new trend. Outdoor areas are starting to come in stronger than ever. Coffee bars also seem to be making an appearance.