Actually these new plans were available a month ago in the app.Airtel has a habit of only showing upto 4 plans on their page. Their app will give the true picture. Right now app is still showing all the old plans abd none of the new ones. Let's see what's the situation in a week when their app will get updated.
1299 Plan showed - 24 Mbps unlimited
1599 Plan showed - 24 Mbps upto 600 GB
But that might be a glitch and they disappeared after a while.