If you apply for a subclass 475 visa before 30th June 2012, all the rules for applying for PR in due course will remain the same as they are now. The proposed changes won't affect you.
If you apply for an sc 475 but later on, before the sc 475 is granted, you decide that you want an sc 176 visa instead, you would have to get a new offer of State sponsorship and then you would have to make a new visa application as well, plus pay new fees.
What is your wife's exact occupation, please? You''ve mentioned "oidl" but I don;t know that that is?