An advantage over you in co-op? Don't get me wrong, I'm no fan of P2W or gameplay-affecting microtransactions in general, but they strike me as more of a "spoiling your own fun" sort of thing when they're not being used against other players.
It really depends on the type of F2P gameplay they make.
- A good F2P: Paying for skins and other aesthetic stuff. You will look cooler but that's about it
- Decent F2P: You can pay for an extra character slot or a bigger inventory. But if you just focus on 1 character you can level him up and get gear for him at the same rate as paying players
- Bad F2P: Upgrading you sword with this +1 damage bonus will take 72 hours. OR you can spend 20 capcom coins and upgrade it now!!
- Bad F2P: To unlock the next skill you need 2000 experience points. Every boss fight will give you around 10xp points. Have fun grinding!!!!. OR you can buy our xp boost pack for just $5.99 and level up NOW.
I guess "advantage" wasn't the right wording. But depending on how they make the game it could be very tedious for f2p players. A lot of F2P games are not designed around the idea of paying a specific amount of money to unlock everything but rather about making the game as tedious as possible with the option to make it all faster by paying. And they are designed so that if you want to constantly get things faster (as you would if it was a normal, $60, game) you will end up paying far more than $60.
So far we can't really know how it will be. But I wouldn't put much faith in the publisher known for constantly using on disc DLC and ending games on a "to be continued" so they can sell you the true ending as DLC