It's hard to say really in terms of downtrend. Some analysts say gold will reach the $1500 range, some say it's going to $3000. There are a lot of mixed views on it right now.
Fundamentally the company is strong. It's withstood some pretty heavy bear markets in the past and has come out as one of the best performers in terms of dividend growth.
The one thing I would say if you do want to add but are worried about the downswing continuing is to average in.
Strictly an example, but going say 1/3 of the amount you'd like to add at the end of every month can lower your average cost per share by quite a bit.