I think the letter should detail the steps & time line you will have.

I went to their website and this popped up

[Public Notice

On January 1, 2016 Touchstone Health HMO, Inc. will no longer offer coverage of Medicare Advantage benefits to our Medicare members in the following service area: Bronx, Queens, Kings, Richmond, New York, Westchester and Orange counties.

If you are a current member, you will no longer be enrolled beginning January 1, 2016.

For additional information, we suggest you call the following numbers:
(hours of operation: 8 am to 8 pm EST) Monday to Friday
1-888-777-0204 (toll free)
711 (TTY)

For help and information about Medicare, please call 1-800-Medicare (1-800-633-4227). Individuals that use a telephone device for the hearing impaired can call 1-877-486-2048. Both numbers may be called 24 hours / 7 days a week.
]
http://www.touchstoneh.com/

If you don't want to wait for the letter you can call the numbers to get details..