Not too sure whether to wait to get it registered on a 60 plate though. If it does arrive before September I'll be itching to get it on the road so may just plump for a 59 plate. hmm 
Welcome

It would be a '10 plate if you decide you can't wait, not '59

Same dilema I had mate... bought a car previously that I registered at the end of July (back when 'Y' reg was about to change to '51')... and realised a few months later that I should have just held off an extra few weeks for the new Reg rather than being impatient.
Had a similar decision for the A500 recently as well, but thankfully managed to find a car in stock unregistered at a local-ish dealer
For you... 2 weeks.. I'd wait for definite. How annoyed will you be 2 weeks later when the '60 plates come out & your 2 week old car looks 6mths old?
I'd say that anything up to 6wks before the new reg is seriously worth considering holding off... unless the dealer is giving serious incentives to register it early.
Anyway... enjoy it when it comes,
Andy.