Originally Posted by Xyro
Whilst you are correct, I don't think it's unreasonable of people to wonder if larger batteries may be available in the months/years after release. Battery technology has got to be one of the more slowly developing areas of technology; we're accustomed to big advances in short periods of time with other things.
Having my fingers in this field, I can tell you that there is nothing better on the horizon that will replace LiPo during the 3-4 year life of the phone (not that most phones are used for that long).
The next big push in Lithium batteries is LiFe which is actually lower density that LiPo and will not help cell phones at all. It is being pushed for hybrid vehicles because it does not have the tendency to catch fire when abused like LiPo does. Search on YouTube for "LiPo battery fires" to see what I am talking about.
It is because of the fire risk that cell phones do not push their LiPo batteries as hard as the RC airplane users do. One of the big risk from the cheap chargers, mislabeled batteries and "change batteries twice a day" regimes is that you may see some fires from cell phone batteries. Hopefully even the cheap chargers are being conservative in their charging algorithms and people are not traumatizing the batteries when changing.
The next thing after LiFe is Lithium Sulfur. That has slightly better energy per volume, but much better energy per weight than LiPo. When that becomes commercially available, it will make cell phone lighter, but will not give much more energy without making the batteries and hence the phones bigger. In either case, you will not be able to use it on your existing cell phones because the voltages are so radically different. You can put a battery and a charger/power-supply in the same package and make it behave like a LiPo but by the time you give up space to that you are looking at the same energy in the package.
There are a few other technologies that are even earlier in the development stages. While they have a lot of promise, promises are all that they are about. It will be years before we know if they are commercially viable and years more before they hit the market in any volume.