I think we can expect that many people will question his statement. Like you, you seem to disagree with it because you think it's too long already only to return to its previous ATH but for a $500k increase, I think I can agree with that since $500k is a massive amount already for just a speculative asset like bitcoin.

Before Saylor came up with that statement, there are already posts here before which states that the bull run can return 2 to 3 years from now and then the potential increase of btc will be $100k. Maybe he only get his inspiration on those posts? Because, sometimes experts do also lurk online especially in this forum to read some information about cryptocurrencies.