Pretty much unavoidable.
Homekit alone hasn't gotten much traction and Apple can't let Alexa run away with the market. Offering up Siri as bait to get develooers to support Homekit is the only option left.
Of course, since it's just a rumor it is doubtful they'll release any hardware this year but, yes,they'll probably announce the Siri move at their next developers conference. It takes time to code all the apps they'll need.
That leaves Microsoft to be heard from. Cortana is coming to XBOX this summer so they'll have a hardware platform to work with but their approach to the Internet of Things is different from Amazon's. Will be interesting to see if they switch.
That "overpriced bluetooth speaker" of Amazon's has certainly made a splash.
