The Germans over at Auto Motor Und Sport state the i9 is an i8 on steroids. Instead of using a three-cylinder motor that barely offers enough power for a lawnmower the i9 will get BMW turbo inline-6 power. Which inline-6 will they use? Hopefully the underrated S55 turbocharged 3.0 liter inline-6 from the new M3/M4.
Additionally, more juice is expected from the electric motors. That likely means heavier batteries and the larger motor itself would be heavier so yes, the i9 would weigh a bit more than the 3380 pounds of the i8. Probably somewhere over the 3500 pound mark which with close to 600 horses and all wheel drive is absolutely fine.
Now, this all sounds great but the real question is will it happen? M stated they want to build a supercar. Some idiot at BMW headquarters said BMW 'i' and 'M' can not mix because he is an idiot and apparently differentiating between two different letters of the alphabet confuses him. A BMW i9 with some serious power to back up the looks is the perfect way for BMW to celebrate 100 years. There is no official word on if it will happen but let's hope the Germans are not just making this report for hits.
BMW, you owe us one. Just give us one freaking car that shows what you can do. 100 years is the perfect excuse to use against whatever accountant says it is too big of an expense to justify. Build the car, show the world just how good you are (were), and fire any accountant or executive against it. There should not be an internal debate on whether an Ultimate Driving Machine should be built. Do it.