A) Meanwhile, Flynn continues giving evidence to the Special Counsel against others, a requirement of his guilty plea, and as Trump "waits," it all keeping building up.
B) Even IF Flynn does get pardoned, he's required by law to testify honestly and fully -- most particularly about the evidence he has been giving to the Special Counsel. (It's sort of hard to say, "I don't remember," when you've already been giving evidence about it all...)
C) A pardon doesn't cover state charges.
D) A good rule of thumb: one should never, not ever, rest your well-being on relying that Donald J. Trump will do what he says and act helpfully on your benefit. This includes if you're Eric, Don Jr, Jared, Melania, and perhaps even Ivanka. A man who gets sued for not paying his bills and who can't even get loans from any U.S. banks because he never repaid them -- and has likely had to borrow instead from Russia and China, one of the very reasons his being investigated in the first place -- just doesn't get a lot of leeway on the "Trust me, I'll help you later" front.