For NSW registered bike
Not all is lost, but you did leave it a bit late.
Your carnet WILL NOT be valid if your bike is not registered.
Steps to take
1. Have a roadworthy done wherever you are to show the bike is roadworthy, eg if in England, have a MOT done or whatever is applicable for the particuar country. If they don't have a system in place, get a reputable dealer to check the bike over and 'declare' it roadworthy.
Equivalent to pink slip in NSW
2. Buy greenslip insurance online for your bike.
3. Arrange with someone in Oz to take your rego renewal that would've been sent to the address where the bike is registered, to a RTA office. Arrange to have the roadworthy faxed to the same RTA office putting a cover note on there saying Mr XXX will pick it up and use it to renew your rego.
5. friend need to send you the new rego. Some countries will not allow you to use the bike if it is not registered.
6. contact the NRMA or AAA (whoever issued/processed the application) in Australia and request an extension.
I have not done this myself, but have researched it because I will be in the same position in 12 months or so.
Hope this helps...and I hope it is really as simple as this (from what I've been told by RTA and AAA/NRMA in Australia)
Remember that this relates to a NSW rego.