They will release it i'm sure. Hopefully they'll release it soon. I started taping QI from series 3, although i messed up on series 4 and i don't know where some are. I want them on dvd. Hopefully they'll release all the series.
It would help boost sales of the first series if the BBC actually advertised the fact that it was available. I can't say I remember them ever mentioning the DVD after the last series which would have been the ideal time.
A remeber a dvd being advertised about once at the end of on episode in the D series, but I don't remember if it was the series or the game.