I think prices will dip, then shoot up 60-80%.
The EU is probably going to withdraw 500 Euro notes. Will this mean that the Euro will increase in value? I think not.

I think numismatic value of Uncirculated (UNC) 500 notes will increase up to 2x

, but after deadline which is at end of 2018.
Banks will give people a grace period to cash in their notes, after which it won't be possible, and will turn to either a collector's item or worthless paper.