If they replaced each of those solar cells with modern photovoltaics, it would provide a ton more electricity to the attraction. If scholarly memory serves, the best efficiency for a photovoltaic on the market in 1980 was like 16%. In 2012, we hit almost 45%. That is an increase of almost 3 times the electricity. This is extremely relevant today, as much or more so than in the late 70s/early 80s.
I always wonder why, with all the green initiatives today, Disney doesn't better highlight the things that EPCOT does. The solar cells on UoE is a great example of a place they should highlight more (and update). The energy produced when Mission: SPACE is spinning down...the water that SSE directs toward the World Showcase Lagoon during storms...rescued manatees at The Living Seas, and other such things. At least the food production in The Land is highlighted, even if it is a small small small percent of the food served at EPCOT. What other theme park in the world grows its own food, generates its own electricity, conserves water, and rescues injured endangered animals, and does it all in plain view of the guests?
Long story short - show me more of the things that makes EPCOT a unique place to visit. Stop trying to make it another MK.