The original femtocell value proposition - the mobile subscriber pays to buy and install the femtocell at her home and also provides the backhaul using her ISP, to get better cell coverage that she's already paying for, is a bit flawed and it's not surprising that femtocells haven't taken the world by storm.
That said, smaller cells, and lots of them, will be needed to provide quality of service in densely populated environments. But carriers will probably have make the initial investment to pay for them.
It may be early days for outdoor small cell development, but the demand has been there for quite some time. And, in the future, the demand will only continue to grow as beefier public and business devices become accustomed to the additional support that they bring. We can expect small cells to become a more ubiquitous part of the device ecosystem.