will i be able to Trade in my IPhone 15 pro max to IPhone 16 pro max when it's released.

This is a user-to-user forum, no one here knows Apple’s plans. You can try asking at an Apple store, or wait until the Next New iPhone is released and ask then.

Apple has not provided any information on an iPhone 16 Trade In Program.

Stay tuned. We'll probably know more in about a month.