Assuming your preferred viewing location is where the TV currently sits, A 'false' corner cabinet with solid doors could be built from the chair rail up & the TV could be mounted to the wall on a pull out, swivel mount. We have our flatscreen TV mounted this way & like it a lot. In your case, it could be easily pushed back into the cabinet when not in use. Lots of different door variations are possible, double doors that fold back, or multi accordion style doors that can be pushed back or even rolled up, down or to the side like the old style roll top desks. This kind of construction could be easily found in many kitchen design centers at your local Lowes, Home Depot, etc. as their frequently used to hide appliances frequently used on countertops, called an appliance garage. A side note; Flatsccreen TV's often come with warnings about being set too close to direct heat sources like fireplaces & woodstoves.