>>1. As, the title of the post asks, how can I tell how overbooked this flight is?<<
One method would be to call Continental and ask. They won't give you specific numbers, but will usually tell you how the flight is in general terms.
<font face="Verdana, Arial, Helvetica, sans-serif" size="2">
Continental Airlines will disclose to a passenger, upon request, whether the flight on which the passenger is ticketed is overbooked if, within the usual and ordinary scope of such employee's work, the information is available to the employee to whom the request is directed. Continental Airlines will also establish and disclose to the customer policies and procedures, including any applicable requirements (such as checkin deadlines), for managing the inability to board all passengers with confirmed reservations.
Our representatives having access to the booking levels of a flight in the normal scope of their duties will disclose to a ticketed customer, upon request, whether the ticketed flight is booked over capacity at the time of the request. Understanding that booking totals change frequently, we will not disclose the specific number of confirmed reservations.</font>
>>2. Assuming that some people forked over miles (and bought more expensive seats) in hopes of a HoKeY upgrade, when do the upgrades clear?<<
Mileage upgrades may clear at anytime prior to 72 hours before the flight. Mileage upgrades to Business
First are not available, without regard to Elite status, within 72 hours of the flight. Standby at the airport is
not permitted.
>>3. If, after the HoKeY upgrades have all cleared, coach is still overbooked, what are my chances as a NW Plat of getting a "complimentary" upgrade?<<
As noted above, on the day of departure, HoKeY upgraders will have zero chance of clearing on a mileage upgrade.
Revenue upgrades are available. As far as an operational upgrade, it is up to the concierge as joebeenyc noted. Anything can, and will, happen. Good luck!