100%, almost. A rupture of the spleen should almost never be fatal, unless there are other injuries in the abdomen with internal bleeding that cannot be controlled.
Other injuries? Most people survive isolated splenic rupture if taken promptly to a major trauma center. However, ruptured spleens are often seen in patients with multiple other injuries (such as rib fractures, pelvic fractures, spinal injuries, and head injuries). Multiple trauma patients have a much lower survival rate depending on the type and extent of organs injured.
Spleen rupture. Surviving a spleen rupture depends on many factors. The most important is how quickly the patient is brought to a trauma center. There are also different degrees of splenic rupture. Many can be treated in x-ray with embolization and blood transfusions and avoid surgery. A severe rupture with heavy bleeding and the patient in shock will usually require emergency surgery.