My question to you forum is:
1. What will happen with Bitcoin when all BTC coins are mined?
2. How will this affect Litecoin and other crypto currencies?
1) Not sure exactly what the question is, but I assume you're asking what miners' incentive to build blocks will be? Answer: transaction fees... Assuming bitcoin continues to exist decades down the road when the last coin will be mined, it will be firmly entrenched as an important and valuable technology/network, and transaction fees will be be quite meaningful in aggregate. Since miners get the transaction fees included in the blocks they generate, they will continue to generate blocks in order to collect these fees.
If your question is more regarding deflationary economics, then the answer is simply that prices will adjust. Price, gdp, and money supply are just parts of the same equation. If economic activity goes up and money supply is fixed, price of goods goes down.
2) It won't affect Litecoin at all, because litecoin likely won't exist. By then, people will have (through many alt-bubbles/pumps/dumps) realized that a coin which offers no real (and quite significant) technical improvement upon bitcoin will not last. Litecoin offers nothing bitcoin doesn't. There *are* theoretically meaningful divergences from bitcoin that could happen, but litecoin isn't one of them. That said, the only even marginally theoretically justified value to litecoin that I can see is acting as a reasonably liquid secondary chain for moving in/out of for various reasons, but I suspect that that role will be taken over by some other coin that *actually* offers something interesting in the end.