That will be a very interesting day
My thinking is that it's bearish. Investors who want to be long Bitcoin can use the futures market instead and not have to worry about all the issues with holding Bitcoin or trusting a Bitcoin broker.
Instead of restricting supply, that will essentially make it unlimited.
The pricing, however, will be interesting:
"CME Group's Bitcoin futures will be cash-settled, based on the CME CF Bitcoin Reference Rate (BRR)which serves as a once-a-day reference rate of the U.S. dollar price of bitcoin. Since November 2016, CME Group and Crypto Facilities Ltd. have calculated and published the BRR, which aggregates the trade flow of major bitcoin spot exchanges during a calculation window into the U.S. Dollar price of one bitcoin as of 4:00 p.m. Londontime. The BRR is designed around the IOSCO Principles for Financial Benchmarks. Bitstamp, GDAX, itBit and Kraken are the constituent exchanges that currently contribute the pricing data for calculating the BRR."
Bitcoin is up 7% today to $10,400.
For more, see the full announcement.