His statement is actually pretty vague... Is he talking about 5-6 years on Mars, Jupiter...? Because, if it's Jupiter years, then I'd say PS5 can easily surpass 300m over that period of time, if it gets continued support and no new consoles are released in the meantime (also, if the industry has not stagnated and collapsed due to the lack of new consoles in such amount of time). But if he's talking about Mars years, then I think it's a bit of a stretch. So, yeah, I need a little more clarification before I can give a better opinion.
Please feel free to correct my English.