1. Will mining become increasingly less profitable in the following years ?
If more people will be using Bitcoins, then there will be more coins to earn in each block = more profit
If Bitcoins will be worth more = more profit
If less people will be mining coins, you will get more coins for mining = more profit
(supposing everything else will stay the same for those examples, a bit simplification)
2. Assuming you have no power costs then when (if not already) will it become unprofitable to mine?
You have to take into account the longevity of your hardware and its cost. If it earns more money during its life cycle than it cost you, it is profitable (although putting your money in the bank or investing in something else might earn you more). You can do your math at:http://tpbitcalc.appspot.com/
3. Does the cpu contribute to mining hashes/s or just the graphics card(s) ?
CPU can contribute, but in most cases it's not much
4. If you are managing your own wallet then how do you go about buying and selling bitcoins ? Could you use a site like mtgox?
Send Bitcoins from your own wallet to the address given by mtgox, sell them there, get money from mtgox to your bank.
5. Lets say you install the bitcoin software on a live cd and generate a bunch of addresses, then how do you copy your wallet (where is the file located).
Probably in the same place as the wallet would normally be (depends on your os)
6. What are the predictions for the value of a bitcoin in the following years?
If you could predict that accurately, you would be rich then;). If people leave it, probably it will go down in value. If people will adopt it, it will gain value. So, do your best and spread the Bitcoin news to everyone you know!;)