When I first heard the 1er was headed to the US I was ecstatic. It could be the spiritual successor to the legendary 2002tii. But, while slimmer, the 1er is not really that much lighter than the new 3. That may not be such a bad thing considering the Z4 rev A is a bit tinny, and a small car with some heft to it will undoubtedly have a better ride. But the calculus gets more difficult when comparing price. A trip to the bmwusa.com car configurator reveals that a similarly configured 135i is about $4k less than the 335i. Not really much of a difference for an entry level car.
Lest you think BMW has gone bonkers, this closeness in pricing is an anomaly peculiar to North America because we enjoy fairly aggressive pricing from BMW NA. Configuring these cars for, say, Australia, it would not be an issue. The person considering the 1er would be saving upwards of $40k over the $108k 335i. What that means is we here in North America have to make a decision about whether or not the 135i is such a significantly different, and better, driving experience that we are willing to pay nearly the same amount for less car. Acknowledging, of course, that the 1er is not a lesser car even though it tips the scales as less car than the 3er.
Only time will tell, but I'm suspecting the 335i will remain the choice for daddy's girls and upwardly mobile boy racers thereby leaving the 135i for purists. I wouldn't be shocked, either, if the 128i becomes the de-facto choice of these purists who may prefer their performance naturally aspirated. Also, the 128i is an excellent candidate for aftermarket modification. Yet whatever happens, one thing is certain, buyers will be buying the 1 because they want one and not because it's a cheaper alternative.