No, that is not possible. Windows RT means it is running on mobile hardware like phones (ARM processors). Windows XP runs on x86 processors (Intel and AMD) so it will not be possible to run Windows XP on a Windows RT device. However, the Surface Pro and other Windows 8 tables (not Windows RT) will be able to run software that was able to run in Windows XP.
You just need to look at Windows 8 tablets (Microsoft's version is called the Surface Pro but others will make them as well) and not Windows RT.