The agreement ends with the purchase in January 2024, so its basically 3 years before Disney owns it all.
With the maximum annual equity contribution of $1.5 billion a year, that means the maximum Comcast will contribute is $500 million a year, and $1.5 Billion over three year. So 1/3rd of the $27.5 valuation, = $9.16 billion, minus $1.5 investment, = $7.67 Billion for something which is worth $4.5 Billion today. It appears by spreading the investment and assumptions around growth, Comcast would plan not to contribute these amounts, and the Disney equity could rise to 79.9%. If this happens Comcast gets $5.78 Billion.
Operational control for Disney means a great deal. Disney can migrate Hulu to the Disney+ BamTech infrastructure. International becomes possible, but there are lots of barriers and costs associated with that expansion (See the link to the interview with the Hulu CEO on the prior page). It can incorporate / consolidate operational savings and advertising synergies. It can also load up Hulu's balance sheet with debt to pay for all of this expansion, which would "water down" the value of Hulu, so the odds that Hulu would be worth more than $27.5 Billion in 3 years to me is pretty low. Disney gets the NBCU content for 3 years, and Hulu on Xfinity for the same duration. The NBCU content becomes cheaper if Comcast decides to place it on it's streaming service, so cost savings.