For example, with your given sample this should work:
sed '/<SrcIntDef>/{N; s/\(>[^<]*<\)\(.*\)\(>[^<]*<\)/\3\2\1/;}' file
But whether that is usable for you depends on more precise specification of what you require exactly and what variations of the input file must be tolerated, for example:
Are the two values that need to be switched always on two adjacent lines or is that variable like xml allows?
Are they in that exact order or is that variable?
Do you want to flip whatever is between those tags?
Do you want the values to flip when they have specific values?
Do you want the values to flip when they have specific values, no matter within what tags they appear?