Last year there were 240 nationally televised games, and if they keep that the same this year, there will be 248 with the 8 more they just added with these ABC Saturday night games.
There's only 1,230 games total, so pretty much the top 20% of games you want to watch are already on national TV and won't be available (so just about every decent game the Warriors, Cavs, Rockets, Clippers, Spurs play).
I think if you look through the schedule, it will be very hard to find a game that's not on national TV that you'd want to pay $6.99 for.
To D.o.s.'s example: there might be a nice battle for the 8th seed late in the season that you want to watch that won't be on national TV, but I think a lot of people who would pay $6.99 for that (the hardcore fans) would have already paid $199.99 for the entire league pass anyways (which comes out to like $0.20 per game). I don't think those casual fans are going to have many enticing options, especially at a $6.99 price point.