Cohen? He's an idiot who played it all wrong. Manafort is playing everything right for a pardon. Cohen blew it until now, but perhaps now is trying to make his best play for a pardon. Here's the thing. Releasing that tape made Trump a permanent enemy, and Trump won't pardon an enemy. Maybe not even for his own survival. However, Cohen's guilty plea may actually be a kind of smart, final, Thomas Schelling kind of move. Remember Tom Schelling? I reference him all the time. The Strategy of Conflict. Sometimes, you have to limit your own choices as a strategic move in order to force another's hand. Cohen pled guilty, and that can't be revoked. He also basically fingered Trump, which... sorrynotsorry for the image. Anyway, since that can't be revoked, and like Beaumont from Jackie Brown, Cohen ain't got a doin' time type of disposition, Cohen knows he'll flip, and Trump knows he'll flip. (Remember the tape?) The only way to keep Cohen from doing more canary-singing vocal gymnastics is to pardon him because Cohen can't undo what he done did.
Will that work? That depends on a) Trump's pride/vindictiveness, and b) what else Cohen has, or at least, what else Trump thinks Cohen has. Remember, Cohen is an idiot. If Trump thinks the little twerp shot his wad, there's no reason to pardon him, and every reason to let him burn for being stupid enough to work for a crook like Donnie and not keeping good enough records to incriminate his boss. You work for a scumbag like Donnie, you keep records to make sure he can't burn you. Otherwise, you get burned.
Notice that none of the scenarios I am drawing out, from either Manafort or Cohen, lead to any real trouble for Trump. Why not? I've said it before, and I'll say it again. Republican presidents are above the law. The Republican Party has decided that it will tolerate any level of corruption, any crime, up to and including potentially treason, if the alternative is potentially accepting a scandal that might hurt the party in an election, thereby giving power to the Democratic Party.
Not everything is zero-sum. Business isn't zero-sum. Contrary to what our idiot President thinks, international trade isn't zero-sum. Elections? Elections are zero-sum, and if you weigh electoral victory above non-corruption so heavily that the most corrupt person imaginable is preferable to the most honest, honorable person imaginable, as long as the former is of your party, you will accept any lie, and lie yourself to cover up corruption in a miasma of bullshit so overwhelming that the electorate cannot distinguish fact from cartoon.
Robert Mueller cannot/will not indict Donald Trump. He will leave it to Congress to impeach, and there will be zero Republican votes to impeach Donald Trump, no matter what Manafort hands him, and no matter what Cohen hands him. Donald Trump is literally unimpeachable. Not in the sense of lack of corruption, but in the sense that it is mathematically impossible to impeach him.
So, why bother to pardon either Manafort or Cohen? He may reward Manafort's loyalty and keep the guy quiet to spare himself embarrassment, while pissing off Mueller and the Democrats. Cohen? That ship has probably sailed, but the guy probably made his best play for a pardon, which was his only choice given how caught he is.