I just came across a Genting presentation from June 22, 2020 that shows the layout of what at least would have been the Universal Studios expansion. This could end up being the design still or it could be downscaled, cancelled, or reimagined at a later date.
As previously reported/rumored, Minion Park would replace the majority of the Madagascar area. In addition Super Nintendo World would replace the rest of Madagascar AND part of the Waterfront area of Resorts World Sentosa:
Minion Park is the orange area and Super Nintendo World is BOTH pink areas:
The main area of Super Nintendo World for guests to explore and interact would go behind (and maybe even in place of) the large 'Resorts World' 'Sentosa' sign which is where Madagascar: A Crate Adventure is now. The Mario Kart ride building which in all of the Super Nintendo Worlds is located either on the side or back of the area would be located here on the other side of the Sentosa Express monorail in what is currently the Waterfront area, specifically replacing the building that has Trick Eye Museum, HeadRock VR, and Malaysian Food Street. As part of the Resorts World Sentosa expansion plans announced last year the "Waterfront Lifestyle Complex" would be redesigned and expanded which is seen in the layouts above. Currently The Forum area leads to S.E.A. Aquarium and from there it is kind of a sharp turn to Waterfront. With this expansion plan a sharp turn would lead straight into the Mario Kart ride building. Now as part of the redesign The Forum area would continue to curve with a wider turn into the new Waterfront Lifestyle Complex which surrounds the Mario Kart ride building. The new Waterfront Lifestyle Complex would extend further into the Meander Shoal and then keep curving into the Sentosa Boardwalk. The part of the Sentosa Express that goes between Madagascar: A Crate Adventure and Waterfront is enclosed by rockwork. Super Nintendo World would potentially involve the rockwork being removed so guests could enter and exit the Mario Kart ride building by going over the monorail. I'm including the aerial photo below from 2017 as reference:
The Resorts World Sentosa expansion as a whole (not Universal expansion specifically) is being designed by RSP (Raglan Squire & Partners) and the long term Sentosa-Brani masterplan is designed by WilkinsonEyre and Grant Associates. The Sentosa-Brani masterplan could and hopefully will involve Universal for further larger scale expansions.
Sources: https://www.genting.com/wp-content/uploads/2020/07/GB-AGM-2020_FINAL_CFO_slides.pdf and https://www.rwsentosa.com/-/media/project/non-gaming/rwsentosa/map/resortsworldsentosa-map.pdf?la=en and https://www.rwsentosa.com/-/media/project/non-gaming/rwsentosa/press-release/pdf/en/2019/20190403-press-release--rws-embarks-on-mega-expansion-plans.pdf and https://rsp.sg/rsp_work/resorts-world-sentosa-expansion/ and https://www.123rf.com/photo_89075322_singapore-november-01-2017-drone-view-of-sentosa-island-resort-a-popular-island-resort-in-singapore.html and https://grant-associates.uk.com/projects/sentosa