AMD did exactly that when their CPUs boosted lower than advertised. And they got away with it. Why not learn from the competition? More important is that it looks like the new CPUs will perform really well no matter the camp. What they're saying in the marketing material is rarely important.
It's common knowledge Intel have struggled really hard trying to shrink. We know this, given the amount of 14nm CPUs they produced. However, each of those had increasingly higher clock speeds.
It's hard to say what sort of frequency they should be hitting now. Mostly because they have struggled so much. Its not something you can exactly put a roadmap on.
However, AMD's Ryzen has been statistically poor since its launch when it comes to clock speeds. What you see is often what you get, with no wiggle room at all for overclocking. So if Intel work on their node what clock speeds can they reach? like I say, it is hard to know.
It's definitely the one thing that has become stagnant, though, so maybe it's what will happen a lot in the future.