More like if there's over 10 you won't get it. Stores will have a minimum of 10 but won't have room for much more if any, so for ANY kind of assurance you have to be one of the first 10 in line (since they're using vouchers). Those TVs are going to be THE killer deal of Black Friday, so you really have to be dedicated, as many others will be too.
These earlier store openings don't help either, since it's a new trend and there's no real precedent to when lines start forming. However, ton more people will be willing to sit there during the day (even on Thanksgiving) to get in at midnight as opposed to sitting all day PLUS overnight until 4am, which is why 7am probably won't cut it this year. You have to one-up them, which is why I recommend being prepared to get there possibly 24 hours early.