Basically, that ship has already sailed, as part of the Great Armada of Digital Disintermediation; unless you're incredibly lucky, exceptionally talented or well connected, your only route to building a profile as a writer is to work for free or for peanuts at least some of the time. Bear in mind also that there's increased competition from other sorts of writers diversifying in order to survive; if you've seen the recent articles about how much novelists in the mid-list actually earn a year (about the same as the minimum wage, basically), you'll understand why so many of the science fiction writers I know also do tech articles and (increasingly) design-fiction work on the side.

That said, while this may be the status quo, that's not to say I approve of it -- and Nature (or rather the conglomerate which owns it) is not exactly short of a bob or two, thanks to the rentier economics of academic publishing. So while I stand by my statement above about the effective necessity of doing some free work, and while flagging this up as strictly my personal opinion, I'd think twice about chasing this particular gig; personally, if I'm going to do cheap or free work, I'd rather do it for an organisation with some sort of ethical justification for not being able to afford to pay me (eg charities or similar).

My two cents, anyway.

Paul Graham Raven