Are standards at IIIT Hyderabad going down?

There is no such proof that the standard at IIT Hyderabad is going down. However, there is proof of their consistency, you can check the round one cut-off of each year below:

You can clearly see that the cutoffs are almost the same from 2017 till now which shows you that IIIT-Hyderabad has maintained its standards since then. 

Also, you might need to know the reasons for the high cutoff to date: No reservation policy, 12th boards marks aren’t required for admission (but a minimum of 60% in PCM is required), The reputation they have built over the years with the placements, academic and research work, Never compromise the quality with the quantity and High emphasis on coding culture and their reputation in that.