text: He said;
  "Government bonds with a 10-year maturity are likely to generate a negative return over the next seven years."
  
  You said;
  " a 10-year bond purchased today would have three years left to maturity, seven years hence. "
  ???
  
  How many (series) of GoC 10 year bonds are there outstanding and available on the secondary market currently Rocky ?
  hint...has to be less than no less than nine (!!)
  How do they differ ?
  hint;several ways
  How many will mature in 7 years ? 
  answer;all of the 2014 series
  What will mature in 3 years...
  the 2010 series
   (what was the coupon at issue and what is the price/yield  now ?)
  etc etc