WADA has the right to appeal any ASADA/AFL sanction. Tampering of the sample regardless of reason will end his career. Either ASADA will sentence him the full penalty, or WADA will appeal and force the full penalty. Again, its surreal some opinions in this thread. like how some people truly believed Gaff would get anything less than eight weeks for breaking Brayshaw's jaw.
So if it is regardless of reason, why on earth did they target test Willie prior to advising him of the tampering infraction (but 2 weeks after the actual incident)?
Clearly they wanted to check whether there were any substances in his system that shouldn't be there and use that information as part of the tampering case. It is certain that if he was found to have steroids, EPO etc in his system he would have got the full 4 years for the tampering (based on the 'proof' that it was a cover-up of performance enhancing substance use) - ASADA can't now just ignore that secondary test (as evidence, not as a charge) because it didn't show up what they wanted to find.
2 years seems about right (possibly even harsh, but I'd guess the penalty will err on the harsher side rather than being too lenient). I'd love 18-months, but don't see that as likely. 12-months or less won't happen as time-served is more than that (and it just opens ASADA/AFL up to litigation down the track - seeing as they have the ability to set the penalty why would they do that)