Chances of successful pregnancy after 2 miscarriages and neonatal death?

Depends. The chances of a successful pregnancy would depend on the reasons for the miscarriages and the neonatal death. Miscarriages are relatively common, but when a women has multiple miscarriages, that can indicate and underlying medical/genetic condition that may make it more difficult to have a normal pregnancy.
Supplements may help. Are you enquiring for yourself, or someone younger? At age 49, there is increased risk of chromosomal anomalies which may lead to miscarriages. Was there a cause identified for the neonatal demise? were studies done to try to determine the cause of multiple miscarriage? In a future pregnancy, you should take 4 mg of folic acid daily prior to becoming pregnant, as will as Vitamin B3 (Niacin).
Hard to day. This situation calls for an evaluation preferably prior to next pregnancy attempt. Genetics, infections, hormones etc can all be worked up to see where the problem may lie.Good luck.