You'll be able to try out the next update to Windows 8—codenamed Blue or 8.1 or whatever you prefer—at the end of June, during Microsoft's BUILD Conference. The public preview will be released then, according to Microsoft.
Windows 8 is coming. But the next version of Windows might not be far behind. According to the super well respected Mary Jo Foley, Microsoft could release the next version of its OS within the next year—a turnaround time that would be pretty much unprecedented for Redmond: