No, the change to MAGI does not affect the size of CHIP Programs.
The number of children in CHIP does not change as a result of MAGI because the new standards have the same value as the old standards; they simply translate the state's pre-MAGI two-step policies into a simpler one-step calculation. For example, if the state under old rules covers children in Medicaid with incomes up to 150% of the Federal Poverty Limit (FPL) and CHIP from 150% to 200% of the FPL, and under MAGI the new Medicaid income standard is 160% of the FPL, that doesn't mean that children between 150% and 160% are losing CHIP coverage--it means that many children between 150% and 160% of the FPL using net income standards were already eligible for Medicaid because of the use of disregards.