In theory that would work but in practice I've found that they still don't quite work correctly.
Some need to compile the program to work. (So they can't work if the code has compile time errors) Some still don't retrieve all the correct candidates for autocompletion.
Also, it's been awhile since I've tried a clang based plugin but I can't recall any of them controlling the syntax highlighting (eg. Show false #ifdef sections similar to comments) or providing a call tree or jump to caller feature.
