Yes, you are almost certainly going to be out of jail long before 48 hours have elapsed. 48 hours is simply the outer realm of what may be reasonable. You will probably get out in just a few hours.
Unless a judge or magistrate is available to arraign you, or you have other holds from different jurisdictions, the police department will likely permit you to post an interim bond or release you on your own recognizance. The police will provide you with a notice to appear in court or a traffic ticket with an "appear by" date on it.
Again, in most cases you will be released within a few hours. Some departments require that you must remain at the jail until you register 0.00 on a PBT. Other police departments require that you stay at the jail for a requisite number of hours based upon your breath alcohol score. Generally, elimination of alcohol is calculated at 0.015 g/100ML per hour, so a person who blows .15 will be required to stay in custody for 5 to 10 hours.
You need to be so sober before the police will release you, since they can't simply let you continue to drive away after a drunk driving arrest. But you have a constitutional right to be free on bond, especially following a warrantless arrest. You have a constitutional right to be arraigned as soon as feasible. In cases other than drunk driving charges, additional consideration are taken into account. For example, in domestic violence cases, Michigan law requires that the defendant be arraigned or held for 20 hours before release.
Jump to the beginning of this article, "Bond, Pretrial Release, JAMs Testing, and Contempt of Court in Michigan DUI Cases."