A quick Google search seems to suggest that unless you hack (pretty extensively) your phone AND install a special hacked version of Skype, it isn't going to work (video calling, that is).
It's entirely possible that Skype will enable this feature for the MyTouch 4G on their own in the foreseeable future, so my advice would be to wait and see -- wouldn't hurt to shoot an email to Skype asking about it either.