Unstrung's Dan Jones has a well encapsulated overview of the possibly options for getting WiMax indoors once it gets rolled out by Sprint.
With the soon to be released Intel chips that offer WiMax on them so the receptivity is resident within laptops, getting the signal indoors is going to be the operators biggest challenge, just like WiFi operators are seeing in the MuniWireless space.
A hybrid WiFi/WiMax solution likely is initially appealing as the installed user base of 802.11b/g/n means the end users are ready. How the broadband gets to them is usually their least concern.
The operators who take the market readiness of the user base into consideration first will be the ones who get users online the quickest, while those who wait for the better technology to come along will likely be left waiting for the users to jump on board.