Let's look at facts. 29 out of the first 58 games at The Rent were sellouts. Only the last 3 years of PP showed only one sellout, Michigan.
Since The Rent has had many sell outs in the past, you have to assume that UConn has left money on the table every time there has been a sell out as they could have sold more tickets. Let's assume that we could sell an average of 15,000 tickets per year based on adding 10,000 additional seats. (Some years we would sell more, some less.) Let's assume we sold them for $30 apiece and you get about $450k of additional seat revenue plus, say an additional $100k in other revenues to total $550k of additional revenues. (This year, we probably would only have sold 10k additional seats as Michigan would have been the only game needing additional seats.)
Also, there is revenue available from other events at The Rent like concerts and soccer which could sell additional seats. (The Rent with a greater capacity would attract better concerts and soccer matches.). Let's assume you could get another $400k to $500k in additional revenues from other events.
Let's estimate that it costs $30 million to add the seats and we invested $10 million (through donations or naming rights in the future) and borrowed $20 million at 3% for an annual interest cost of $600k which means its in the ballpark. Even if it costs an additional $10 to $15 million to add the seats, it's still in the ballpark. And, making UConn more attractive to a P5 conference is worth $10 to $40 million per year in additional revenues.
The time is now to do it with interest rates low and to make UConn a more attractive option to P5 conferences.