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