The larger the battery market becomes, the more competition it will attract. Tesla is certainly starting off with a nice lead, but it would be foolish to underestimate the capabilities of other players who might just not be interested enough in this market yet, and who'll -- for the moment -- happily have Tesla serve as a canary.

I'm not entirely sure if Tesla's battery tech is a sufficient differentiator.

Tesla is a slave to the Lithium Ion process of Panasonic. If a new chemistry breakthrough comes out tomorrow (ie: Redox Flow has huge potential in the utility space, even if it has little potential in the retail space)... Panasonic will be able to switch to the new chemistry but Tesla's battery tech is basically Lithium Ion only.

Tesla's battery technology is literally the battery electronics. Not the chemical cells. Tesla seems to employ chemical experts so that their battery-electronics can better predict the effects of the chemistry... but really... they're only putting together cells. Tesla doesn't make the 18650, Panasonic does. Tesla just puts a bunch of 18650 together, as well as have some sort of algorithm to make them charge / discharge at high efficiency.

Tesla is completely dependent on Panasonic's chemistry. The speed at which LG was able to build a "Silicon-Lithium Ion" battery pack of GM's Bolt only demonstrates how "easy" the battery-pack problem is.

And as solar gets cheaper and cheaper, there's only going to be more incentive to install batteries.