sure, if there would be a better world with an equal initial position for all market players and always balanced businesses. But this wont be so. Most likely some people and organizations will own pretty much Bitcoins and many will not own any Bitcoins.
And there will be most likely a bank system and private loans from very (bitcoin-) rich to the (bitcoin-) poor. And there will be a significant amount of interest to pay but where to take from? I think all over the world today with normal money this problem is solved with inflation (money printing and loss in value of money). But this impossible with Bitcoin.
May be a solution is the simultaneously use of Dollar, Euro ... (I'm not sure). But this means: Bitcoin system depends on the existence of regular, traditional money.
"To return later they will have to buy the Bitcoins from lenders, who will have Bitcoins from the first loanees." Ok. but if the lender don't sell the Bitcoins and only lend this? Then you have to lend additionally Bitcoins to pay the Bitcoin interest rates - and next year there are more Bitcoins you don't havo for paying back.
"Another possibility is to pay in rates - earlier rates go the circulation (market) and you get them (buy or earn) again to pay next rates."
Ok, and if the lender don't sell the Bitcoins ...