Immortality is not yet possible, however many scientists who work on life extension research say that we will be able to stop aging within next 30 years, and some are even more optimistic than that. This means that people that are alive today and are younger than 50 years-old have pretty good chance of making it alive and becoming immortal. However, in order to make sure you don't die too early you need to take step of precaution to make sure that you will survive until immortality will become possible
After anti-aging and life extension treatments will become available people will not just become immortal overnight. It will start by extening our lifespan few years at a time, until we will be able to fix all age related damages in our body at which point biological immortality will become possible. But it will not end there. For what we know, we will have to do anti-aging treatment all the time, to remove new damages. In practise this will mean that you will have to either constantly take medicine and/or attend anti-aging treatments for example every 10 years. However further in the future it will be possible that nanobots inserted in us will automatically clean our body continuously and we won't have to worry about it anymore.