I have bought the 5.6 any change for a upgradeBrowser Info Environment
I am not going to buy all my already paid for add-ons again!
first, thanks for your interest.
Concrete 5.7.1 and the new marketplace integration just went live on Friday, so everything's pretty new.
I do have in mind offering some sort of upgrade option or a special offer for users who already bought the 5.6 theme.
The new version of the theme has some new features (such as support for layouts and multiple pages), and costs $30 instead of $25. Anyway, I see your point, and I think that a special upgrade offer would be fair.
This week I'll look at the available options in the new marketplace and make a decision.
(You see, this is the first theme available in the new marketplace, I've already asked the core team for advice on this)