Sorry, it's your premise that EA Sports will have to support Switch after whatever happens with MS could eliminate their consumer audience on Xbox?
I don't see your math adding up.
Madden buyers have plenty of options to get their product, and they have historically not considered a Nintendo platform their preferred choice since probably the Super Nintendo? (Even then, maybe only Madden '95? I don't see a sales comparison but EA Sports fans were primarily on Genesis in the 16-bit era.) Conversely, Nintendo fans have a record of not turning up for sports games, and it has not improved over time. EA tried authentic releases, they tried cheaper'ish Legacy Edition releases, they tried custom-made "kiddie" or "waggle-control" versions of sports game, they tried their arcade-style BIG sports games with Mario characters in them, but nothing sustained in sales... and meanwhile, even Nintendo has made its own sports games (including producing titles promoting a professional team they had a vested interest in) but those franchises didn't last either.
The idea that Madden Xbox fans, abandoned by Xbox, (assuming the whole Xbox ecosystem just vanishes with the upcoming announcement, which isn't what rumors of the announcement are saying is coming but let's go with it or let's say their supposed open-platform concept is a non-starter,) will turn to Switch instead of a PlayStation or a PC or a streaming platform or whatever other way to get their NFL fix, that doesn't seem likely. They could have bought portable sports games in the past on and they chose not to (or, when they did choose to do so, they did it on PSP or Vita, whereas the more popular Nintendo DS and 3DS platforms did not proportionally prove more successful in sports game sales.) And Nintendo players could have bought sports games (not Madden, which stopped with Wii U, but Switch has had NBA 2K and FIFA/FC and MBL The Show and a few other games; recently the arcade-style Wild Card Football was released in 2023,) but they had other preferred genres.
EA isn't stupid; they have the data, and if sports games sold bucketloads on Switch, they would make them, even if they had to get a separate development team to do it. However, despite the number of Switch hardware pieces sold, not enough Switch gamers buy sports games. (There is a bit of catch-22 scenario, where Nintendo platform games usually get lesser versions of sports games and so consumers don't buy them and then devs make even lesser versions because nobody bought them, and the cycle spins down. However, in pretty much all cases, an authentic version was released first before cutbacks started happening; FC 2024 for Switch was a full redo after many Legacy Editions of FIFA built on the customized Switch FIFA 17, we'll see if or how long it is before EA has to cut back Switch versions.)
Maybe Switch 2 will refresh the audience and sports will do better? Maybe the Xbox shakeup will push some players into considering Nintendo's ecosystem? Maybe some things will change in the future. But as far as EA Sports regretting decisions regarding not supporting Switch hard enough up until now, they've already crunched the numbers and they have learned that Smash Bros don't buy Madden.