If we somehow get Xavier specs, which is at least 1.3 TFLOPs docked with 138GB/s bandwidth and 8GB RAM, it will be very very close to base PS4, with mixed precision mode and it's newer technology and tools.
1.3TFLOPs Xavier currently runs at 20-30 watts at 12nm. If we could get it down to 10nm or 7nm, I think it's doable. The main thing is running 400-500 GFLOPs in handheld mode with 3 hrs battery and not over heating, which is 2.5x-3x current handheld specs, and I think that may be doable with 7-10nm node.16nm TX2 already runs 50% faster as the same watt usage as TX1/Switch, and that doesn't include the 20nm heat throttling issue that made the TX1 only run about 80% of the proposed 500 GFLOPs, which is apparently only unique to the 20nm node. So in theory, 750 GFLOPs docked/300 GFLOPs handheld should be just as energy efficient as current switch. We'll see. For all we know, Nintendo could have two handheld modes, with the first being current switch handheld clockspeeds with the current docked bandwidth to save battery life is using 300TFLOPs.
But knowing Nintendo, who knows. If we do get a hybrid hardware upgrade, I see it being anywhere in the 600 GFLOPS- 1.3 TFLOPs GPU range for docked mode.