I think, in the future; scientists and doctors will be able to replace your old, used cells, will new healthy ones. Although we can replace bones and It's even possible to have an artificial heart and lungs. It's your brain that keeps you going and it will eventually... wear out.
I'm no scientist or doctor, But I believe the human body is very well made, we can repair our cells very well. As long as we are healthy and can cure the big things in our life e.g; broken bones, diseases. I think our bodies have the possibilities to renew cells.
Here's a list of some things humans can fix:
Broken Bones: Can be fixed from a cast, or even pins and metal
Eyes: Your vision may fade, but that's due to the lense on your eye getting de-shaped, this can be cured with laser eye surgery. I have also seen a documentary on a lady who was blind, they managed to connect the electrons inside her eye, via microscopic 'things' which allowed to be able to see black & white again
Heart: If your heart begins to deteriorate, there IS official hearts which can keep you going, which while your artificial heart is in, they can be finding you a new one.
Lungs: There IS artificial lungs
Tumors: Can be removed
Cancers: Scientists are finding new ways to kill certain types of cancers, I think in the future, cancer will be easy to kill.
Brain: This is where it's hard... you're brain isn't something you can temporarily remove or anything, ALTHOUGH, it is proven; Your body
does regenerate brain cells just like your bodies system does with other cells.
There is many other things which aren't curable at
THIS TIME But think about it... future.... It's forever really, there is so much time so there WILL be immortality some time.
An immortal existence would be sad and lonely one. Watching those around you slowly fade from memory while you remain alone would be hard psychologically. But that doesn't even bring in the medical effects of living to such an old age. Your vital organs will eventually go, unless you have them transplanted from something else, as there is no way you can prevent them detioriorating from extreme age. I am also fairly sure that once your blood gets to a certain point it stops functioning properly too.
Who sais this? it's more people give up and
THINK they are old, there are stories of people who are at the age of 100+ and are still active. It's about keeping fit and healthy no matter what age you are at. Some people, when they reach the age of 60+ think they have to retire and just sit at home, when they can really be out and about doing things.
I doubt immortality will EVER be open to the general public. Can you imagine population? It would be more densely populated than china everywhere.
By the time immortality is 'released' It's more then likely we would have migrated to other planets, especially seeing as how humans are evolving in technology these days... In the past 100 years, humans have evolved computers from being a 1 tonne machine to being a hand held little chip, which stores alot of information. We have sent robots to planets which roam around there, powered by solar energy. Really, there is no limits.
Humans aren't built to give up, anyone that believes there will NEVER be immortality or wont even think of the fact of moving to other planets... well... they should. The universe is endless and there is no limits
These facts considered, what do you think will happen within your lifetime? What do you think your actual lifetime will be?
I'm not going to give up

I'm going to stay active for as long as I live, I'm going to stay as fit as I can and not give up just because I'm old. Just to stay a regular happy person, till the day I day (that's my goal anyway)
Anyway, there's alot more I wanted to say... But meh