So what is the percentage going to be after 25% of this year (after May 2016)
Well the annual inflation rate and the APR 'interest' rate you can earn through staking are two different things under the new staking calculation of the coming codebase which removes the 'coin-age' and variable reward of the existing system.
For example, if the first year on the new codebase provides for a set block reward which equates to a 3% increase in the total number of coins after 12 months, the second year would still have the same number of coins being added as the first, due to there being the same number of blocks being produced, but the total coins in circulation would have increased, thereby resulting in a slight reduction in annual inflation for the second year of just below 3% and will continue reducing each year after that.
As of now people are able to leave their wallets switched off yet still receive an accumulated staking reward which is based on coin-age, thereby providing them with an amount of coins as though they had been staking the entire time, which is hardly fair. The new staking calculation rewards the same number of coins per block, meaning that if 10% of all the wallets are staking, they will each receive a proportional share of the total coins being issued. So there is a variable interest rate over the 12 months based on how much staking you do. If 10% of the coins are staked, they will earn a 30% APR but it still produces exactly the same number of coins added to the count each year.
You can thank Rat4 of Blackcoin for realising how to fix the inherently unfair and somewhat insecure (coin-age being able to be accumulated and lend excessive 'weight' to an attacking node is a potential security issue in standard PoS) previous models of staking.
http://blackcoin.co/blackcoin-pos-protocol-v2-whitepaper.pdf
With this new method there is incentive to stake continuously, thereby providing for a stronger network.
So, to answer your question, the new Bitstarcoin codebase is likely to go with a fixed block reward which will be equivalent to 3% inflation in the first year, offering the variation in APR for each staking wallet as discussed. This isn't completely finalised yet but is likely at this stage.
