Hi there
I'm currently studying B Arts with the Psych major and I'm planning to transfer into the B Arts-Psychology course next year
From what I know, their structure for the Psychology courses have changed quite a lot, and basically in order to do any Postgrad in Psychology at Macquarie, you will need to do the Honours year, so as Asylum mentioned it should be 4 years before continuing to become a registered psychologist
you can check it out here
http://www.psy.mq.edu.au/courses/pdf/2013_Psychology_Pathways_to_registration_Flowchart.pdf
So yea, Macquarie seems to have made it harder to get into Postgraduate Psychology courses with the 4th Honours year becoming a requirement, whereas beforehand you could have completed something along the lines of a Graduate Certificate.
The main difference between the Psychology course and the Psych Major, is that the major is not accredited for any further postgrad work/registration as a psychologist, whereas with the Psychology course you can continue with further studies and become registered
Either way, it is absolutely fine to get into the B Arts with the Psych major, and then transfer into the full B Arts- Psych course after a semester, so no need to worry as long as you are committed to the course