Overall, I'm largely ambivalent, trending to concern. While not at all as certain as to the fate awaiting DF, I do understand much of Blind Wolf's skepticism, and share some of it as well (especially when it comes to deals with publishers).
Well, obvious upside includes an influx new players (and community members), many of which will be paying up front.
But, see, I'm worried what sort of precedent this sets for the current donors. As soon as there's a price tag, there will be those who will not be as willing to give as they have already. These players will undoubtedly compare what they gave to what's being sold, and, like any consumers, determine if they've got their value's worth or not, and whether its still worthwhile to continue such donations. For DF to remain sustainable longterm, there will both have to be enough buyers, and for an uncertain amount of donors to not change their donation habit negatively.
I'm also unnerved as to how this will affect roguelike development as a whole. More specifically, whether this will continue the trend of other such passion projects to become products. Dwarf Fortress before was, in my eyes, one of few sturdy pillars standing against corporate expansion in such niche gaming. Now that its got a publisher for the purpose of monetization (even if in limited respects), that can no longer be said to be true.
We can only wait and see if this change is for the better. It's a profound change. I don't envy the Adams brothers their decision, nor blame them, given their circumstances. I just hope they haven't unintentionally let out the demons on this one...
EDIT: As a less gloomy aside, I'm at least a bit mollified that prominent Bay12 regulars like Meph are involved.