My subscription (membership?) still has time left on it, but I'd like to take advantage of the "Gobble" sale and upgrade (renew?) SONAR Platinum for $99....would that simply be tacked onto the time I have left and extend it another year from that date, or would my new year begin upon purchase?  Like I said, probably a stupid question, yet I ask it anyway.

http://forum.cakewalk.com/Renewing-membership-with-time-remaining-on-existing-one-m3321371.aspx
 

The thing is, I am in the store now, have the upgrade in my cart and have applied the discount to make it $99 so that's odd.

The thing is, you shouldn't be looking to upgrade since the upgrades are for X3 and before.
You should be renewing, which looks like it's not available yet. I think if you pull the trigger on that upgrade you just might be flushing $$$ down the drain.
Here is a quote from cakewalk staff in the link that was posted by gustabo.
 
"There will be a clear path for renewal/upgrades in January for people like yourself. There is no option to buy another 12 months right now."