If you own one of the current generation of Echo Show devices, not only will you be able to use Alexa Plus, you'll also be one of the first to access it as part of an early roll-out program. The Echo Show devices with early Alexa Plus access are:

Amazon has unveiled Alexa Plus and while it’s rolling out to Echo Show smart displays first, most Echo smart speakers will also be supported.

Alexa Plus is here but it's only supported by four Echo products as of now, and won't be supported by more than half a dozen Echo devices.