The 4000 series may draw more power on average, but because they have a process advantage (30 series was 8nm samsung, this is gonna be 5nm I think) they'll actually be more efficient. For example, the latest rumor is that the 4090 has the same TDP as the 3090 TI for twice the performance. Here's a little table.
SKU PERF POWER(W) WATT/1%PERF
3090 100% 350 3.5
3090TI 110% 450 4.1
4090 200% 450 2.25
So basically the 4090 is actually 50% more efficient than the 3090, it just also draws more power in absolute terms.
Therefore if you're worried about the power draw of 4000 series GPUs you'll just buy further down the stack and ultimately still end up with a better product. The same thing happened last GPU generation too. The 3070 for instance has basically the same TDP as the 2080 but produces significantly better performance (~15% uplift).
What to expect: the 4070 will perform better/equal to the 3080 at the same/less power. Expect it to be more expensive than the 3070, but still cheaper than the 3080. This will generally hold true across the entire generation.