BMW platforms (body styles) are usually made for six years. There's usually a mid-life refresh after three years. Yeah, your F30 330i is the previous body style, but it was also that after just one year. Buying or leasing the last year of a platform can often get you a better deal, by the way. I personally think the F30 looks better than the G20. I also think having a BMW that is two-platforms old and still in good shape is a status symbol, a sign of diligence and intelligence.
Your car's probably worth about $35k now. That's probably way more than the residual. I'd bet your residual is below $30k.
It sound's like you have the SUV itch and the new BMW itch. Powerful itches have to be scratched. I'm with you on having all those gadgets. I pretty much check off every box when I'm ordering a BMW.
One of the boxes you should really think about checking off on your new X3 is the $150 spare tire. It raises the floor of the cargo area about seven inches, but you won't miss it. It also brings the floor up above the rear hatch opening. That actually makes it a lot easier to get heavy objects out, because you don't have to lift them up over the hatch opening. You really need a spare tire on a road trip, even with run-flat tires. Just ask this F25 X3 owner...
(680) The cost of no spare tire! | BimmerFest BMW Forum
Having a spare tire will also give you the option of going to non-run-flat tires when the OE tires are worn out. They're usually cheaper, ride much better, and also last longer.
There's a shortage of 19" X3 wheels as the X3 factory. So, a lot of X3's are coming with 20" summer performance tires. Those summer tires will make the car completely undrivable in snow, even with xDrive. I'm assuming you get snow where you live, since you currently have an xDrive BMW. The best way to deal with this is have two sets of tires and wheels, one for winter, one for the rest of the year. A set of winter tires and BMW wheels will cost between $2k and $3.5k, if you can even get them. There might also be shortage of 19" BMW wheels for the winter tire packages. If you're going to lease, you might be able to get them included as part of the lease contract.
Also, does it pay to get the bigger engine because it will have a better resale down the road in 6-7 years if I plan to get into something else ?
No. That's just car salesman talk. They've been saying that since before I was a yoot and went with my mom to buy her 1972 Plymouth Fury III. The M40i is probably $5k more than a 30i. Don't expect to get much of that money back in resale. Also, if gasoline goes to $6/gallon that would hurt the value of big-engine cars.
When things were normal, a good rule of thumb for depreciation of a car driven 12k miles/year is:
25% down from MSRP the first year.
20% down from the previous year's book value the year the warranty ends, the year the car becomes seven model years old, and the year the car goes over 100k miles.
15% down from the previous year's book value the remaining years.
So, expect a six year old car to be worth about 30% of MSRP and a seven year old car to be worth about 25% of MSRP. Options depreciate faster and sometimes further. That extra $5k for the M40i might get you back around $1500.
Test drive both a 30i and an M40i. That's the only way to decide if you need ~380 h.p. instead of just ~250 h.p.