Yes, if you earn the next 25k in 2014 then it goes towards 2015. It does not add to the PQM from 2013 to get you to gold.
Jan 1 2014 your PQM will go back to zero and you start over. You maintain your silver status till Jan 31 2015 but if you want to be silver the rest of the year you must fly 25k before then.