Many begonias, including the 'beefsteak' ones, are seasonal bloomers. You've done a good job growing this, and you'll probably get bloom the end of winter/early spring. They sometimes need a bit of a dormant season--cooler and drier--in the winter, and bloom when they're getting ready to start growth again.

That is right. Almost all rhizomatous will bloom in early spring after a winter's rest. Not all will bloom though which may be the hybrid or some other environmental reason. I had two pots of erythrophylla (beefsteak). The biggest pot did not bloom, yet the smaller pot did. Both were in the same conditions - same size pot, same kind of light, etc. Go figure.