With the right hub, you'll be able to expand your system dramatically without things getting too complicated.
Typically, a hub will include multiple radios for popular smart home protocols like Z-Wave and ZigBee -- the wireless "languages" of smart home gadgetry. This allows the hub to "talk" to everything in its native language, then translate that info into a Wi-Fi signal that you (and your router) can understand and put to use. With the right hub, you'll be able to expand your system dramatically without things getting too complicated.