Sorry to tell you this but if that is the official position of your company then it is already too late. Senior management has made their position clear simply by taking this stand. They have shown themselves to be short-sighted and uninformed of basic human motivations.
Regardless of how you find to "turn it around", your top talent will be leaving within three months, followed quickly by the experienced staff. After the first few key people leave, the company will start offering incentives to keep those that remain. The incentives will work on a few people for a while, but eventually they will leave as well.
Over the course of the next two years, you will only be left with the workers who are easily bullied into working unpaid overtime. Needless to say, this isn't the group of people that you can draw leaders from. Of those that remain, they will start incorporating more of their personal lives into their daily work (they have to since they have less personal time now and things need to get done) so they will put in 48 hours, but only be productive for 38-42, if that. Did I forget to mention that efficiency studies of the IT field have shown that the performance gap between skilled/experienced workers and those less experienced can be as high as a factor of 10? Yep, that's right, those that remain will take a lot longer to get the same work done.
The overall quality of all work done by the company will fall - fast. Clients will notice it and start shifting business away to companies that can get the job done right. Managers talk to each other and word will spread quickly. Before long, the only business the company can get are projects that are radically under-bid, counting on the "free" time from the staff to make up for the low bid.
At this point, the environment at the company will be so poisoned that even the people that were bullied into staying will start leaving.
To put it another way: "Been there, done that"
Let me explain why this happens with a lesson from Capitalism 51. Company X pays $75,000 for a specific job. Company Y down the street also pays $75,000 for the same job but requires that everyone work an extra day. Which company will have to work three times as hard to hire and then keep people? Which company is more likely to be able to hire the top talent?
The fact that you are here asking this question means that you care about your job and about the company which is good. It means that you most likely fall into one of the top two groups I discussed. If your company doesn't drop this policy fast, I suggest that your plan to "turn it around" involve outbound resumes.
I'm sorry to sound so negative, but this 48 hour idea isn't exactly new.