It's probably a year or two out, at least. They want the Steam Deck 2 to be a proper power jump from the original, and there hasn't been any significant hardware improvements that would allow that yet.
Other handhelds have more power, but they do that by dumping way more power into the chipset for increasingly small returns. It's not really worth it to make a new Steam Deck with one of those chipsets because you would be trading off most of the battery life for any power increase.