The exchange rate 1BTCD=50KMD will be the same for all the period of the swap (1 year) ?
Basically yes, but the exchange rate will decrease slightly every day to account the 5% APR bitcoindark has. With this we ensure there won't be more BTCD than there are KMD reserved for the swap.
So apparently there isnt any difference partecipating the ICO (as i done) and buying now BTCD and wait the swap?