"Provided that
it shall be mandatory for all the distributors of television channels to either discontinue or modify all their existing packs, plans or bouquets in compliance with the provisions of these regulations after 31st January, 2019."
TRAI has not said that existing packs can be continued as they are. It has said that existing packs have to be modified or canceled on Jan 31. So, if you think buying a 1-year pack will give you protection for 1 year, you are sorely mistaken and a nasty surprise is in store for you on Feb 1.
If you're wondering where it has said it, it is in Gazette Notification --
https://main.trai.gov.in/sites/default/files/Regulations28122018_0.pdf