From my understanding, you are only allowed 1 PPOR, however there can be a 6 month 'cross over' while you transfer from one to the other, as in your example.
As the new property you bought will be tenanted from day one, then unfortunately there will be CGT implications when you sell, regardless of whether it was intended to be your PPOR or not.
This will be apportioned between the time you rented it, and the time you lived in it as your PPOR.
This is definitely something you should get your accountant to discuss with you, to work out the best strategy.
If you do plan on selling in the future, you may be better off requesting vacant possession on settlement, and forgo any rent, so you don't trigger a CGT liability.