No just no. Every single Dice game was 900p 60FPS on PS4, I seriously doubt they could improve the engine that much to do 1080p 60FPS.

Also the game will definitely not be a 4k title on PS4 Pro and certainly not Scorpio either as MS doesn't allow the framerate to be lower than on the regular X1 version, which for Dice games is 60 FPS at 720p.

Actually, it could hit 60fps if they prioritized that, theres nothing about the game as a game that is that demanding.  People need to wrap their heads around the fact that it's the engine and the systems (that is, what goes on in the game) that determines how difficult it is to scale, not graphics.  Because if the engine has integrated scalability tools and such, the graphics issue is easily resolved.  Systems - things like AI, physics simulation, etc - can be the bigger challenge, especially if said systems are integral to the game's function.  The first EA Battlefront certainly did not have such complex and demanding systems, it was the graphics pretty much exclusively that sucked up the juice as the real meat and potatoes of how the game works is even simpler than your average CoD and definitely simpler than Battlefield.

So the question here is really quite simple: when they upgraded Frostbite for use in next gen games, did they do it in such a way that scaling back down in the area of graphics is very difficult (I would hope they are not this stupid) or did they just enhance what COULD be done, adding another level of capabilities.  If the latter, a Switch version would be far less difficult than people seem to think, assuming this game doesn't add a whole lot of demmanding systems the first did not have, which I doubt it will.

You are right, it would be capable of hitting 60fps on Switch if it was engineered that way.

But there would likely be some massive compromises in order to achieve that Target. 30fps would be a far more realistic target whilst having a degree of fidelity.

Frostbite itself hasn't been overhauled significantly since the last gen consoles. I am still able to play Battlefield 4, Hardline and Battlefield 1 on a 10 year old PC with similar performance levels.
Frostbite does extremely well on anemic and old CPU's as well, always has, so the Switch has that going for it.

They wouldn't need to improve the engine, just scale back the visuals.  Doubt they will but they could.