Of course espionage will be in the game. It is a crucial part in warfare and Hearts of Iron 3 had it in aswell.
It is embedded in the diplomacy screen as you can see in the screenshot below. Keep in mind that the menu most likely isnt final and some options may werent even in that built at the time or simply were deactivated since they were not finished. I would guess that military espionage and tech espionage was disabled or something like that since there is room for 2 more options without the need for scrolling.
There is no Intelligence in the way there was in HOI3. No spies etc. because no leadership value to divide between tech research, diplomats and spies. And no Intelligence UI.
A couple of the options that could be done from Intelligence in HOI3 can be done from Diplomacy in HOI4, agreed. But this is very much more limited, like Boost Party Popularity. And, although it doesn't show in the UI, I would imagine this costs Political Points, not spies.
There is space on the Diplomacy UI in the screenshot, but that could be because the country in question - Iran - is not a puppet/colony of Italy. I would expect some options to release/create puppets. And they may have given themselves some leeway for future expansion packs.
I don't believe that Intelligence options were removed from the menu and deactivated. The game was almost ready for Alpha to be approved when the media event in the UK happened. I don't believe they could have submitted the game in a state where one of the major interfaces was that unfinished. And with no screenshots/videos giving any hint of HOI3-like Intelligence, I believe it has been cut.
The only suggestion of "espionage" was the enemy discovering your battle plans. But I wonder now if that was wishful thinking on our part, or if confirmed by the devs, that this may have been dropped later. It is now about a year since they first announced the battle plans.
Maybe Intelligence will appear in a future expansion, but not in vanilla.