The console is deactivated for the demo, and we (those of us who do not have beta access) don't know what they will be. Fear not, however, as I am quite certain that you will quickly find a full list of cheats on the forums once the game comes out.
I like to play (at first) without cheats to see how the game is really designed to be played.
Eventually however, my favorite play-throughs all use mods and cheats to advance an evolving "narrative" that I have in mind as I go through the game. I look forward to seeing a well developed cheat list in the coming weeks for exactly that reason.
Some other very useful ones kept from EU3 is the tag feature, and the annex feature. In the console, type "tag [Insert country ID here]" to change the country you are playing as. You can also type "annex [Insert country ID in FULL CAPS here]" to immediately annex the country. I have tested it and you may have to repeat the annex command twice to get the desired effect. The country ID is a 3 letter version of the country name. So England is ENG, Castille is CAS, Ottomans is TUR, etc. If you can't find out the ID of the country you want to swap to or annex, you have to go into your EU4 folder (in steam), go to common, then history, then countries, and it gives you a list of notepad files, titled with the country ID, and then the country name. Hope this helps, and please don't get addicted to cheating like I have.