No, as soon as you create an XML Mapping you have to store the information in the database. The other problem you have is that you can't show any type of "variable" in a form.
You can solve the first problem by calling the webservice using a java action, with your own custom call (for an example of what the call should look like, set the loglevel to debug for webservices to true) and then return the value you parsed from the resulting XML to the Microflow as a variable.
As for the other problem, you could show a popup containing the value, but not a real form.