Consoles typically run at a static clock speed, no power saving beyond shutting down idle cores. The rumor actually has been for around 3 ghz.
This is definitely true, though I think there are going to be good reasons for this to change.
At 8C/16T, 3Ghz may be quite a bit of TDP (in terms of the overall budget at 7nm in a smallish console box). In isolation, obviously it would have plenty of room to do so even without exotic cooling such as in the X1X.
However, they're also seemingly cramming a 14.2TF Navi custom GPU into the APU, and wanting that to be clocked as highly as possible in contrast to the CPU portion, as that's by far what will make it impressive visually, while even at ~2Ghz, a Ryzen2 is an absolutely monumental improvement over Jag.
Finally, in terms of what has come before :
PS2/OG Xbox/GC/Wii, were all far too old and low power to worry about power/heat.
PS3 had Cell+RSX, and ~2005-era didn't have much in the way of power modes really, besides, the 8 cell 'cores' were also frequently used as extra graphics compute (eg; with Naughty Dog titles most notably). So no real need or ease of implementation for power states here.
X360 had a similar situation with PS3, gen7 you pretty much wanted your max CPU anyway, so no power modes.
PS4/X1, now we're talking a gen where it could have come in handy. Well that is, if they hadn't gone with the ultimate potato processor. Even maxed out at 1.6 (PS4), 1.75 (X1), 1.83 (X1S), 2.1 (Pro), or 2.3 (X1X), there was never really room to give up any CPU performance. They were essentially 8-Core netbook ultra low power processors, designed to fit into little tiny mobiles and tablets, and the potential savings would be nominal if any, at the cost of going from atrocious performance to completely unacceptable performance.
Now with Ryzen2 sharing space with a sizable Navi portion, you're talking a full fat desktop CPU that calculates out to a pretty reasonable performance level, and with a bit of extra power draw at higher clocks. Of course we also know that game code often gets into situations where one or two cores are extremely loaded, while others are nearly idling. Or, you have some background OS/friends list/minor tasks that don't need full performance from a core/thread.
I'm not saying 100% that it will have modular power states such as per core turbo/dynamic clocks, but it would honestly surprise me if it didn't, for two reasons :
It would allow for quieter/cooler/more efficient use, thus also being more reliable with less constant full clock heat.
It would allow for more effective use of a given TDP. Eg; 4 threads @ 3.4Ghz, 8 threads @ 2.2Ghz, 4 threads at 1.4Ghz, in a given example where draw/need was strongest and weakest. As long as the thermal design is capable of running all 8C at some reasonable max if absolutely necessary (albeit possibly with some extra fan noise), I think this is a good way of setting it up.
Just my thoughts, YMMV