BARCELONA—Within 30 years, artificial intelligence will be smarter than the human brain.

That is according to Masayoshi Son, chief executive of SoftBank Group Corp., who says that supersmart robots will outnumber humans and more than a trillion objects will be connected to the internet within three decades.

These beliefs underpin the wave of large and surprising deals the Japanese internet and telecommunications company has pulled off in the past year, he said Monday. These include starting a $100 billion technology-investment fund with a Saudi sovereign-wealth fund, buying British microprocessor designer ARM Holdings PLC for $32 billion and acquiring U.S. asset manager Fortress Investment Group PLC for $3.3 billion.

This 30-year forecast created urgency, Mr. Son said in a speech at the telecom industry’s biggest trade show, Mobile World Congress. “That is why I’m in a hurry to aggregate cash to invest.”

In a brief interview after his speech, Mr. Son said his $100 billion project with the Saudis, dubbed the SoftBank Vision Fund, was bigger than the $65 billion in combined investments from the venture-capital world. He said the SoftBank Vision Fund would be focused. “Artificial intelligence, Internet of Things, smart robots: Those are the three main things I’m interested in,” he said.