First of all you should understand the fact that no branch has a bleak future every branch of engineering is equally important going by example of the branches mentioned in your question energy crisis and development of sustainable energy is the need of the hour nd is very important in future hence energy science is a good branch looking at future as well on he other hand any invention of mankind has the first step in its designing and is managed by design engineers so it also has great future hence its upto you which branch you want to pursue as both are equally good and important for future.