If there's anything BMW excels at these days, it's expanding their lineup. While some of their products have been questionable from a design perspective, you have to at least give them credit for innovating and trying new things. That goes for the "i" family too.
BMW, as you probably know, has trademarked all sorts of fancy new names, including i1 through i9. But based on some BMW execs' comments at the Detroit Auto Show, an i5 or something similar could be next.