November will be too late to apply, especially if you're seeking January entry. ESF CSS (
http://www.esf.edu.hk/admission) only starts in January so it will be too early now, but you can (and should) always call to put your name down. The problem with all those new P1 programs at preschool is, that all these children still need a P2 spot at some point. Yes, some will leave HKG, but a lot of them will need spots, and most schools will only have a very limited number of spots from one year level to another, so it doesn't become easier. So therefore, I always advice to look into "less popular" schools as well (the international ones on the island are very very popular plus the entire ESF and AISHK) that don't just offer a P1 year but where your child could stay in case the wait is longer than just that P1 year. I have no idea about wait lists at schools like AIS, JIS, HLYIS, NIS which are all in the New Territories. Then there is Delia School of Canada, Korean International, CAIS (not sure where they are), Harbour School, etc. These schools seem (slightly at least) less popular than ESF, HKIS, FIS, GSIS, CNDIS, HKA, etc.
You will need to act ASAP and get your child's name down at a variety of schools. And yes, your child will be the youngest in his class in ESF. By the time you arrive, the Y1s are halfway through already and due to enter Y2 in August. Holding back is sometimes a possibility but Y1 places are hugely over-subscribed (last year close to 3,000 spots for slightly over 1,000 spots).