BMW's lineup of 3-series alternatives is growing, and with it some non-traditional derivatives for the brand beginning with the number 4.

Although the recent buzz in Los Angeles was about BMW's X5 M and X6 M, we were equally curious about the 4-series Gran Coupe and X4, which stood alongside the South Carolina-built SUV and crossover.

We recently caught up with Hildegard Wortmann, senior vice president for product management of automobiles and aftersales, and Carsten Pries, head of product management for BMW's M division.

For Pries, who manages all things M, the overarching question was whether an M4 Gran Coupe would make sense in the lineup, given that it now includes an M3 sedan and an M4 coupe.

His answer? Not going to happen.

"The M3 is an important brand that has heritage as a four-door car," Pries said. "If we would now put an M4 Gran Coupe on the market—which would also have four doors—that would be most probably some substitution which doesn't make too much sense."

His answer is in line with the dictum delivered to us earlier this year from a product line manager, but it falls out of step with the 5-series and 6-series derivatives—which comprise an M5 sedan, an M6 coupe, and an M6 Gran Coupe.

As for an X4 M, however, product manager Victor Leleu "couldn't comment."

According to Wortmann, the proliferation of models under the 4-series family makes good business sense, too.

"We have lots of customers who really want to go into this four-door thing, but they still want to have the elegance and the beauty of a coupe," she said. "As long as this principle works, and we're doing something valid to the business on the one hand, on the other hand it's really [authentic], then there's nothing wrong in doing it."

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