...I haven't gotten all of my keys/passphrases yet.
I was a little surprised to see a public key along with a passcode and Lisk account number from my XCR deposit. Is this public key the same as the one in discussions going like "please send me 1 XCR so I can get a public key" ? Will we need to do a "first transaction" in our new Lisk accounts in a few weeks to generate a new public key, or is the one assigned at the ICO site a good public key forever?
In asymmetric cryptography (public-key cryptography) a pair of keys is used (public and private). Both keys are generated simultaneously.
With the "first transaction" you mentioned, the public key is not generated, but firstly stored in the blockchain.