While by the time immortality could become wide-spread, should research be taken in that direction, the big problem at the moment is food supply.
In short, within the next 100 years we will reach a critical mass where our population with surpass our planet's food production.
We're closing in on it now. There's only so much arable land available. There's some hope for using GM (genetically modified) crops to alleviate some of the problem, but consider...
Do you like hamburgers? I do. And yet beef is hugely wasteful given the input-output of foodstuffs. One acre of soy produces as much food as 18 acres used to raise cattle (Modern Marvels, gotta love History channel). In addition soy doesn't require that we feed it with edible foodstuffs that we could be consuming ourselves (though it would be a lower quality of product, it's still food). Raising cattle does.
How about the push for bio-diesel engines? The amount of corn required to produce enough bio-diesel to fill one gas tank is equivalent to that required to feed a person for one year.
We have issues with food supply now, never mind if/when they start granting immortality. If our explosive population growth is left unchecked... (and I know that thinking along those lines has horrifying implications)
Now, with that said, onto the immortality.
I've mixed feelings about it. Would I like to live forever? At the moment, sure. In 4 million years, probably not so much. I feel that at some point ennui would set it. Crushing boredom from the 'been there, done that' mentality that comes when you do the same thing, over and over and over. For a time there would be plenty to do. But eventually you'll have done/read/experienced everything. And even exploring space, which could well be something that takes eternity, wouldn't be the answer; unless they also perfect cryogenics (or something with the same effect) you'd be awake for the entire trip. Hundreds of thousands of year, stuck in a small space...
Then again, immortality would allow us the chance for some real long-term planning. Projects that take centuries to complete, overseen by the same group. One mind having the time to fully explore every aspect of something. The ability to watch the far-reaching repercussions of our actions.
Then again, the possibility of tyrannical regimes spanning millenia. Thousand-year Reiches under the same dictator. Million-year-old televangelists...
"It [death] is the most profound experience of any creature." -Frank Herbert, God Emperor of Dune pg 239