Defensively Pillar has been great and more than expected. I think his contributions with the glove make him an excellent 4th outfielder.
His offensive performance this year and his speed on the basepaths make him a suitable regular.
Personally, I would like to trade him while his value is sky high, but I highly doubt there are teams out there that will be paying a lot for a guy like Pillar.
You don't have to look far to see a similar player in this franchise' history - Reed Johnson. He had an insane 4.4 war year but never touched close to it ever again.
That being said, I think the Jays have the depth in Pompey to take a risk and carry Pillar next year.