All rhododendrons develop woody stems with age. The photo shows nothing that would indicate this one is dying. In fact, it looks perfectly normal and healthy.

Usually old rhododendrons become leggy and produce only sparse blooms because they have become increasingly shaded by other plants over time. Increasing the amount of sunlight they receive by cutting back the growth that's shading them is the best cure. A soil test would also reveal any nutritional problems, although old rhododendrons with extensive root system rarely need fertilizer.

Radically cutting back an old rhododendron is an iffy proposition. Sometimes it works fine, especially if the plant receives enough sun, but it can also fail miserably. A safer course would be to cut back 1/3 and see how it goes. If it sprouts from the pruned areas, prune another 1/3 the followinng year, etc. It will, however, be many years before you're likely to see much bloom.