Longer you wait after the rider training course, more you will realize that you are forgetting. Not necessarily how to ride or riding techniques but mostly all the info and tips that they keep feeding you during the course. I wish I could get my first bike as I got my M2, but I had to wait for two months to put the $$ together, and I was surprised how I forgot some things so fast in those 2months.
As number two, if you are considering buying a used i.e Ninja, they are quite hard to find during spring. And if you do find the right bike that you want, the prices are much higher than it is at the moment.
For last, I know this now after riding for 6K kms this season since June; if I didnt have a bike, I would work 24-7 to put the money together until I have enough to walk out from moto shop with a bike =) First priority really lol so I would get my first bike even if it was November now, just for the possibility of few days of riding. Last season there were people riding in January ! A few days it was around 6Celsius.
Get it now, you won't regret it for sure !!!! It will def help you keep the instructions at moto course alive in your memory over the winter.