"watch this space" meaning in English

{
  "etymology_text": "A 19th century formula, originally placed by magazines in space which was reserved by an advertiser but for which no advertisement was ever submitted.",
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "phrase"
      },
      "expansion": "watch this space",
      "name": "head"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "phrase",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English imperative sentences",
          "parents": [
            "Imperative sentences",
            "Sentences"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "examples": [
        {
          "bold_text_offsets": [
            [
              130,
              146
            ]
          ],
          "ref": "1979 November 7, The Australian Women's Weekly, page 115, column 2:",
          "text": "I fully intend to ask the talented Mr Peng to give me simplified instructions for making some of his fiery Hunan specialities; so watch this space.",
          "type": "quote"
        },
        {
          "bold_text_offsets": [
            [
              98,
              114
            ]
          ],
          "ref": "2012 November 12, Torres News, Thursday Island, page 21, column 1:",
          "text": "\"We all look forward to the next walk in 2013 which we all hope to be a bigger and better event - watch this space!\"",
          "type": "quote"
        }
      ],
      "glosses": [
        "An indication that a development will follow."
      ],
      "id": "en-watch_this_space-en-phrase-LHavkrS7",
      "links": [
        [
          "indication",
          "indication#English"
        ],
        [
          "development",
          "development#English"
        ],
        [
          "follow",
          "follow#English"
        ]
      ],
      "raw_glosses": [
        "(idiomatic) An indication that a development will follow."
      ],
      "related": [
        {
          "word": "film at 11"
        },
        {
          "word": "stay tuned"
        }
      ],
      "tags": [
        "idiomatic"
      ]
    }
  ],
  "sounds": [
    {
      "audio": "En-au-watch this space.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/d/d0/En-au-watch_this_space.ogg/En-au-watch_this_space.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/d/d0/En-au-watch_this_space.ogg"
    }
  ],
  "word": "watch this space"
}

{
  "etymology_text": "A 19th century formula, originally placed by magazines in space which was reserved by an advertiser but for which no advertisement was ever submitted.",
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "phrase"
      },
      "expansion": "watch this space",
      "name": "head"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "phrase",
  "related": [
    {
      "word": "film at 11"
    },
    {
      "word": "stay tuned"
    }
  ],
  "senses": [
    {
      "categories": [
        "English entries with incorrect language header",
        "English idioms",
        "English imperative sentences",
        "English lemmas",
        "English multiword terms",
        "English phrases",
        "English terms with quotations",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "examples": [
        {
          "bold_text_offsets": [
            [
              130,
              146
            ]
          ],
          "ref": "1979 November 7, The Australian Women's Weekly, page 115, column 2:",
          "text": "I fully intend to ask the talented Mr Peng to give me simplified instructions for making some of his fiery Hunan specialities; so watch this space.",
          "type": "quote"
        },
        {
          "bold_text_offsets": [
            [
              98,
              114
            ]
          ],
          "ref": "2012 November 12, Torres News, Thursday Island, page 21, column 1:",
          "text": "\"We all look forward to the next walk in 2013 which we all hope to be a bigger and better event - watch this space!\"",
          "type": "quote"
        }
      ],
      "glosses": [
        "An indication that a development will follow."
      ],
      "links": [
        [
          "indication",
          "indication#English"
        ],
        [
          "development",
          "development#English"
        ],
        [
          "follow",
          "follow#English"
        ]
      ],
      "raw_glosses": [
        "(idiomatic) An indication that a development will follow."
      ],
      "tags": [
        "idiomatic"
      ]
    }
  ],
  "sounds": [
    {
      "audio": "En-au-watch this space.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/d/d0/En-au-watch_this_space.ogg/En-au-watch_this_space.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/d/d0/En-au-watch_this_space.ogg"
    }
  ],
  "word": "watch this space"
}

{
  "called_from": "form_descriptions/1089",
  "msg": "suspicious unhandled suffix in English: 'film at 11', originally 'film at 11'",
  "path": [
    "watch this space"
  ],
  "section": "English",
  "subsection": "phrase",
  "title": "watch this space",
  "trace": ""
}