"A 720p or 1080i with MPEG4 uses approx 4GB / 60min. Most Movies are under 150min which means 9.4GB is more than ample for a HD movie"
you're not accounting for the extra space used by the newer audio esp lossless,
which if i recall correctly can max at 18mbit/s (dolby hd)
a long movie (ROTK EE 251 mins) will consume quite a bit
as for many longer TV series (roughly 42 mins per episode).
at your projected bitrates (4GB / 60 mins) this won't fit on a single disc
without sacrificing quality to some degree
Lost S01 ....... 24 Eps
Westwing S06 .22 Eps
CSI S05..........25 Eps
~920 to 1050 mins of showtime per season, and that is excluding extra stuff.