In my experience, after about three weeks, fermentation is usually done. I would give it a few extra days, just to be sure, then proceed with your original plan.
How does it taste?
I'll add that attenuation was about 70%. White Labs lists this strain as attenuating between 78-85%. The under attenuation could be the result of underpitching, fermentation temperate, oxygenation level, and/or wort fermentability.