I think it will be back. It was routine back in the day and I don't see why people wouldn't do it now. I believe one of the upgrade sellers did mention in a post somewhere around here that the value of the gold will be taken account for the price of an upgrade
For instance, lets say 1m = 1$
An upgrade = $4.50
So you would have to pay 4500k or 4.5m for an upgrade.
Only thing I'm wondering about is if people are going to keep the gold for themselves or in a way find it more time consuming seeing as they aren't just receiving money, but yet have to sell what they received from a previous trade, which would make it 2x longer possibly?