^^^ It is a very packed schedule for India, although there is a possibility that the Asia Cup (which is originally scheduled for June 2021) will be postponed to next year. The selectors need to rotate the players (especially the bowlers) in order to avoid burnout. With such crowded schedule, there is a real chance that a lot of the players will face injury issues. The India tour of Sri Lanka will immediately follow the IPL 2021.
Same story every year, Indian team is cash cow for BCCI and other boards so their schedule is heavily packed no matter what. I think we're are going to see rotation policy soon for all 3 format. Majority of premiere player might get fair amount of rest during SL/Zim and Asia cup if it happens.
It is the truth, and BCCI is one among the richest sports organization in the world. Possibly this heavily packed schedule will lead to three separate squad for T20, ODI and test format. Only then players will get proper rest. Anyhow with BCCI, players are being paid good and that's the reason why players are very eager to play for leagues like IPL than other similar leagues on different countries.