Are there more tribe seasons after season 5?

Answer 1

Not yet, and they aren't called seasons either.

In Britain a television "series" is a set number of episodes that have been budgeted and planned for in a set period of time.

After a series has ended, they may or may not be renewed as a new series.

Tribes has had 5 series (not seasons).

Its doubtful that they will have more as it's now been off the air for a number of years, but its not impossible.

Red Dwarf for example had 10 series but they were broadcast over a period of 20 years with several years off in between some of them and less than 1 season or year of time between others.

Doctor Who another British series has had series running on and off for 50 years with more than 10 years gap (skipping the entirety of the 1990's) before coming back on the air with another series in 2005.

British television simply does not follow the "seasons" pattern of US television and series have been known to stay off the air for years before getting renewed.