I believe Wikipedia has a flawed business model. It depends primarily on donation.
I am sure many donate; but not that many. Businesses cannot work on donations. Only NGOs can. And Wikipedia is clearly not an NGO.
Paid subscription seems to be an obvious way. This is the Encyclopedia Britannica model. I am not sure this is going to be hugely successful. The Wikipedia is a collaborative effort, so I cannot see a contributor ready to pay for using the wiki. In fact, it is more likely that a contributor will demand payment.
On the other hand, a collaboration with Google could actually rake in moolah. Google can place context-based advertisements in the wiki and share the revenue with Wikipedia and the contributors. This might actually reverse the loss in the number of contributors reported recently in the news (see here)