I'm sure there will be some limit, but until the chips are available for testing, we won't know what to expect in real world conditions. TDP will be the limiter, but what that specifically translates to in clock rate i have no idea yet. However, even a conservative 10% above boost would be quite nice without pushing it too hard.
Got confirmation that not every Ryzen CPU will have this capability. Will be limited to the ones with "X" in the model number.
Here's a pricing/spec table:
ryzentable.JPG