It's impossible to tell exactly how an individual rhododendron will respond to cutting back in the manner you propose. Growth at the tips with bare stems below usually indicates too little light. Under this condition, it will be difficult for new growth to sprout from the bare remaining stems. A better technique is to cut back in stages. One third this year, one third the next, etc. if you get no regrowth from the first pruning you can then leave things as they are, or move the plant to a sunnier location.

Here are some photos of the