Doctors dream of having artificial blood always on hand, but the reality has usually been very different. While you can produce red blood cells in a lab, the current technique (which prods stem cells into action) only nets a small number of them at best. British researchers appear to have found the solution, however: they've developed a technique that can reliably produce an unlimited number of red blood cells. The trick is to create "immortalized" premature red blood cells that you can culture as much as you like, making mass production a real possibility.
The biggest challenge is translating the technique to commercial manufacturing. Scientists have produced a few liters of blood in the lab, but there's a big difference between that and the massive volumes needed to serve even a single hospital. Although the UK's National Health Service is planning to trial artificial blood this year, this new technique won't be involved.
As it is, you wouldn't likely see a wholesale switch to artificial blood even if this new method was ready for the real world. Any mass production is most likely to focus on people with rare blood types that can't always count on donations. Even that limited effort could make a huge difference, mind you. Hospitals could always have a consistent supply of rare blood, so you wouldn't have to worry about them running out in a life-or-death situation.