I remember seeing some old shows about small passageways that we have yet to explore, and a possible room/repository near the sphinx. Is there anything that we "know" should be in either but have yet to find, or anything interesting that we suspect might be uncovered in the future? Do we expect to find any other major archaeological sites in the area (tombs, small pyramids, etc)?
The Giza Plateau was used (and still is) as a cemetery for at least the last 5,000 years.
It encompasses 12 pyramids, dozens of rock-cut tombs, hundreds of mastabas and chapels and temples, serdabs, and statues.
Although most of the buildings are documented at least in some rudimentary form (often by multiple archeologists) there are still many new discoveries to be made.
Most prominent examples:
A satellite pyramid of Khufu was discovered in ~1992.
A large pyramid town was unearthed that could house a few thousand people. (a few hundred meters south of the Sphinx)
Recent discoveries:
In the last few years the pyramid town of Khentkaus I was re-excavated and precisely documented.
A medium sized harbor and a silo was found south of the town.
Modern research and excavation take time and are expensive.
Funds are short and are preferably used for unexcaved/poorly explored sites instead of reexamining the same buildings over and over again.