I will spend three weeks in Wollongong Dec 18th - Jan 9th.
Is it any idea to bring a speedboard and some rigs (from Europe) during that time?
Or put it this way, how big is the chance to sail over 40 knots in NSW or SA during that time?

no sure about wollongong but Rick cracked 39 last week in sydney
lets hope for a great summer .. i say if England are getting such cold weather we may get real hot this summer so bring on the NE stars !!
but saying that ... the last few moths more top speeds have been done on Formula
:-)
for sure it will be a dam site warmer here !! so hope you have a great time in the Gong
I think u will sail more slalom 5.8- 6.7- 7.8 if theres a day that is a cracker i have an old sputnik speed board you can borrow just add straps

Bring at least a smallish slalom board. Gerroa is bound to have a good couple of blows over that time. Closer to Wollongong, Kanahooka point on lake Illawarra is also pretty windy in a noreaster.