I think it will work like fantasy football trading:
Some people will take advantage of people that know a lot less. Or people that are desperate and willing to pay real world money.
Some people will constantly talk about trading, but the trade they want will be a maxed dragonite for their mid range Delibird, because it was a limited spawn. In other words, a steal for them, and not a trade.
Most trades will be gifts from advanced players to their friends.
And very, very rarely, more rare than a perfect shiny, you'll find someone who actually wants to negotiate fair value.
And can you imagine the "Should I make this trade" posts? Success in trading might even become the new meta.