What is "watch this space"

phr. (context idiomatic English) An indication that a development will follow.

Watch This Space was a short-lived Australian children's science fiction television series which ran on the Australian Broadcasting Corporation from 7 April to 13 June 1982. The show starred Paul Chubb, in his first leading role on a television series, as a red skinned alien named Rufus who arrives on Earth and attempts to break into show business. The alien is helped by a local man, played by co-star Ron Blanchard, who attempts to help him fit in including helping disguise his spaceship as a normal home and later moved in with him as a roommate.

Being largely unaware of Earth culture, the alien would regularly become involved in comical social situations. This was most often as his human friend's expense who, while receiving weekly visitors, continually tries to explain away his odd behavior and the existence of his talking shipboard computer. Other actors who appeared on the series included local bands, performers and celebrity guest stars such as Steve Bisley, Liddy Clark, Jon English, Rebecca Gilling, Tracy Mann and Kris McQuade.