At $20,000/per, great where you have backhaul and power. Capex budgets are artificially constrained at most telcos. Wall Street is demanding higher dividends and lower capex, even where irrational. Verizon, AT&T, Vodafone and Telefonica have all reassured the street they will keep capex down. 

Small cells have been the next big thing for years, but I haven't seen many of them. Christos Karmis of Mobilitie tells me that's changing dramatically in 2016 and with a salesman's enthusiasm predicts 1,000,000 by 2020. Sprint is planning 70,000 small cells, while Verizon and T-Mobile have talked big plans.

Some will be indoors, more likely to be called Distributed Antenna Systems (DAS,) especially in large buildings impractical to fully cover from outside. Some of those outdoors will also be called DAS, some counted as cell sites. From here on, cell site figures will be impossible to compare. Capex budgets will become even fuzzier than they are today. Many of the small cells, indoor and out, are being installed by third parties like Mobilitie.

 Telcos can increase capacity with small cells (densification); putting more spectrum to use (carrier aggregation); adding antennas (MIMO and Massive MIMO); network sharing; and half a dozen other techniques. Verizon, Sprint, & T-Mobile claimed they've doubled speeds by adding a second, 20 MHz carrier. Deutsche Telekom just announced a field test with 5 carriers for over a gig. Softbank has deployed 43 cell sites with 128 antenna Massive MIMO, claiming an improvement of 6-10x. Somewhere around 2022-2025, highband 5G will become a common choice. Verizon will bring highband to the field in 2017 or 2018, but few expect significant volume before next decade.

 Everyone has a different opinion on which will be dominant. The answer is "none." Different telcos will make different choices in different locations. Softbank in Japan jumped ahead on Massive MIMO. Masa-san is fearless about new technology and new sites in Japanese cities are difficult. Softbank owned Sprint may go first to 4 & 5 carrier aggregation. They have over 100 MHz in most U.S. cities currently unused. Verizon will jump ahead with 5G highband to replace some totally obsolete DSL. It's great pr, even if the actual build will be small for years. 

Karmis has installed small cells at the Kentucky Derby (200,000 seats,) major buildings, and sports arenas. He works with all the major carriers so is well informed. It was a pleasure to talk with him. In 40 minutes, he gave me clear answers to a slew of questions in a field I didn't know well. 

The real experts- the CTOs of the major companies - will tell you they aren't sure.