How can I predict, 8 weeks post upper and lower blepharoplasty, whether under-eye "pouch" is swelling or permanent? (photo0

You are still early and things are too difficult to tell based on photos and not an exam.  Be patient for another month and take time to discuss your concerns with your PS.  You may need some finetuning but take time to discuss with your PS.

Thank you for the question and included photos. It is hard to say if you are still swollen at need an enhancement at this point. Wait a few more months before judging the results. Hopefully, it looks fine then. If you are dissatisfied, your surgeon can do a little touch up. Good luck.

What type of surgery did he do?  Fat excision?  You do still have some swelling or residual fat there.  It can take 4-6 months to resolve completely, so you need to be patient.  However, from the appearance here, I would be that you may need a revision or some HA filler into the tear trough to smooth things out.    

I would say that you need some time for things to heal. It can take some more time and the difference you are seeing now may resolve completely. I would let it heal more and by 12-16 weeks have a better sense what is going on.