…? Whether you should buy out now or later? There is no stock answer, it depends on the math in your situation.
You don’t have to even think about extending until the end of September. You didn’t tell us your MF, I suspect it’s lower than a used car finance rate would be now, but anything you do will be at a higher rate.
When you buyout, you’ll owe sales tax (could be rolled into a loan potentially), and if you do so near disposition you will likely also need to renew your registration.
If you’re keeping the car, you can request your payoff from BMW and send them payment. Check your local bank and CU, there is a thread here about purchase rates.
If you want something more hands-on:
Your car came with a 4y/50k factory warranty, you can purchase an extended warranty if you think you will own it past that point.
If you like the 330e I’d probably keep it, refinance the buyout with my bank or CU closer to disposition (Halloween) and set a reminder to check about the warranty every 6 months to decide if I need to do something about it. I don’t see a reason in your case to extend the lease 2 more months if you’re going to buy it.