Cross-post of information I obtained from Joost de Vries about the fix for the fogging issue (huge kudos to Kimbal for putting me in touch with the right people!):
I just had very useful series of e-mail exchanges with Kimbal Musk, George B, and Joost de Vries concerning the new ventilation ducts. The gist of the information is below.
I must say that I have been thoroughly impressed by the level of interaction these three busy individuals have shown in addressing my concerns, taking the time to reply promptly and personally to a single customer. I made sure to note this in my replies to them.
Quoted from Joost de Vries:
"Regarding the windshield defroster functionality (or lack thereof), we got the 1st prototype parts last week and we have been testing them in a –30c cold weather chamber to make sure they will do the job. The good news is they do and we should have parts available late next week. I have requested my Service Managers to start reaching out to existing customers in the affected areas to schedule a service appointment to do the change. For new vehicle builds into Canada it will be a Service fix before delivery as the final production tooling will kick off only later this year. The retrofit on the defrosting is pretty straightforward. We loosen the A pillar trims left and right, lift out the dashboard top, remove the mesh screen. Insert the new directional air flow pieces, install the new mesh screen and reassembly the dashboard top and A pillar trim. It'll be less than an hour work. I am confident our customers will regard this issue as resolved once they experience the new venting system."