A can of worms might be an understatement.
New non-B&O televisions now feature multiple HDMI, and USB socket connections. All that I have seen in Europe, North America, and Asia still have RCA connections in back, on the side, or both. A number also have an antennae connection, memory card slots, DVI, AVI, component and composite connections.
In non-B&O, mass-produced televisons, it is only the price that has dropped, and not the features. Your options with any new televison has increased.
Having pulled a few kilometres of cables through conduit in masonry walls, I know how difficult that work can be, especially the drilling. While it was enjoyable in tropical Brasil, it was not much so in the Suisse Winter of 2009.
You mention that you are not interested in HD or 3-D, and if I understand, you wish to retain the B&O 9000 and AV 7000 for sound. Am I right then in thinking you do not have Masterlink cable connection, a Beoport, or Internet sound sources ? It would be helpful to know a bit more information as to what exactly you have (cables) in the walls, and under the house.
I agree with you regarding 3-D, as that evolving technology is in it's infancy, but HD is another matter. It is sharper, more clear, and easier on the eyes if one views a lot of television, DVD, and also does computer work using the same monitor.
I would not easily dismiss the opportunity of a new HD television, as it can easily work well using your system. Any HD television could easily connect to your system using an HDMI to AVI or DVI adapter for HD video, with your stereo sound remaining as before.
If you have digital cable service available to you, your solution is very simple. HDMI from your cable-box, Sat TV-box, or set--box dout irectly to your television, with sound-out option then out from your television via your current cables, to your 9000 system.