Is that possible to upgrade HTC wildfire s os? Is that possible to update the HTC wildfire s OS from Gingerbread to some other higher versions.
See this previous question: When will my phone get the Android 2.3 update (Gingerbread)?, according to that HTC have announced that the Wildfire won't be officially updated to Android 2.3 or newer as it doesn't meet the minimum requirements for the newer operating system versions (in particular its CPU runs slower than 1GHz).

There are unofficial upgrade options, as noted in that question CyanogenMod 7.1 supported the Wildfire. This question, How do I update the OS on my device? goes into some of those options.