It's highly unlikely a next-gen Switch would hit 4TF. Those chips can hit upwards of 60W at max clocks. If Switch 2 uses Orin, it will definitely use the cut-down NX version with significantly reduced clocks to hit 15W when docked. You can check Orin specs here: https://developer.nvidia.com/embedded/jetson-orinnVidia Orin is releasing this year, with Ampere arch. And it has 2048 cuda cores and 64 tensor units.
It's a 4 TFLOP SoC, that can also do DLSS.
Nvidia has already announced Atlan, in 2021, as it's next SoC.
By 2024-2025, any of these can be used by Nintendo, and still be more powerful than the Steam Deck.
The Jetson Orin NX 8GB version has:
1024 cuda cores
32 tensor cores delivering 70 tops
765 MHz max clocks (remember that at max clocks this chip still uses 20W as shown in the specs page, so it would be likely underclocked)
6-core Arm® Cortex®-A78AE v8.2 at a max clock of 2GHZ (likely underclocked as well)
102.4 GB/s LPDDR5
While theoretically Nintendo could also achieve 15w with the full versions of the chip, it's unlikely they would choose them, and even if they did, the clocks would have to be reduced A LOT to reach 15W, so there's no way in they could ever achieve 4TFs at 15W.
I don't know how many Tflops this NX chip would have theoretically, but even if it reached something like 2Tflops, we have to also remember that RDNA 2 compares favorably to Ampere flop for flop. For instance, 6900xt and 3090 have similar gaming performance, but the AMD card has 23 TFlops while the Nvidia card has 35.5 Tflops. Feel free to do the math on the difference.
I can see Nintendo coming up with something with similar performance that uses less power. The Steam Deck uses 25W for the whole unit, while Switch currently uses around 15W docked and around 9W portably. I highly doubt they would have something more powerful if they went with Orin, especially considering they absolutely would not release a console with a mere 1h:30m~ battery life like the Steam Deck, however, if they choose something newer, they might release something faster.
Also remember Ampere competes with RDNA2, so if Nintendo chooses it in the future, it will still be competing with similar tech to what the Steam Deck has right now.