your trs will not actually run out on your current property.
you will get trs until 31/12/17
"year 8 and thereafter at 15% Ceiling 3,000 Ending 31/12/2017"
If you are not a First Time Buyer and you purchase ( top up ) in 2012 you will only receive TRS at a rate of 10% on a ceiling of 3,000 up to 31/12/2017.
you will need to start claiming trs in 2012 for the new property so you will have to move ppr next year to facilitate this.
so if you stay put with your ppr
you will get 15% of 3000 until 31/12/17
if you move ppr
you will get 10% of 3000 until 31/12/17