I think it really depends on the surviving dogs personality and your wishes. Some dogs really do well as an only dog and even seem to enjoy being the center of attention. Some really enjoy interacting with other dogs are better off in a multi dog home.
I think a couple good questions to ask yourself are:
1) Does your dog's play well with other dogs that do not live in your home? This will give you an idea of what the introductory period would be like.
2) Does your dog do ok around puppies and are you ready to raise a puppy? This will help you figure out if you would be better off adopting an adult dog.
3) Do YOU want another dog? This is the most important question. You should not get a dog for your other older dog you should get another dog because you want one and have the time and energy it takes to introduce a new dog into your household.
If you do decide that you are good to get another dog spend time now thinking about what personality would work best. It generally works best to get a dog that matches the existing dogs energy level and play style. Size matters too... having dogs of drastically different sizes can cause problems as the big dog may be to rough or accidentally hurt a much smaller dog. Once you get to the point of actually selecting a dog, if you are getting an adult dog have them meet before you fall in love with the new dog. This meeting can tell you a lot about if their personalities will work together.