Central air would certainly be a selling point, but it is difficult for anyone to say whether or not you would recoup your money or not because it depends on what the overall housing market does over the next 5 years.
You would get to enjoy the use of the central air system over the next 5 years though so you should factor that into your decision. Are you using a bunch of old outdated window units now? If so, a more modern energy efficient central air unit might save you money in electricity. It could be beneficial to check for the availability of state programs as you might be able to get some incentives for the upgrade. For instance, in Massachusetts there is a program called mass save at http://www.masssave.com that offers incentives for energy efficient upgrades to homes.... more