The borders will remain open, the Border Patrol will be chasing coyotes and tumbleweeds with those high tech motion sensors, and even if the "Virtual Fence" works (which it won't, and the folks proposing it know that), Guest Worker euchers the whole project. So now mass flows of cheap, unprotected labor will be here legally, ensuring that employers don't even have to worry about INS.
Guest workers will legally have anchor babies, and immigration will expand.
Silver lining: lots more Catholics.
Depressing defeatist as usual...when will you learn.