Google has confirmed that Allo for Web will be released soon. The confirmation came in the form of a tweet from Amit Fulay, who is Head of Product (Allo and Duo) at Google. Specifically, he said the application will be made available in a "few more weeks."
On it ... few more weeks— Amit Fulay (@amitfulay) July 8, 2017
Back in February this year, Google’s Nick Fox tweeted a sneak peak of the web-based client, saying that it's in early development phase. He, however, didn't provide any specific launch time-frame. But now it's reasonable to assume that the application will be released sooner than later.
No idea of migrating to Allo from WhatsApp. If they bring desktop access for Duo, then could consider that. Giving the same offer for WhatsApp too for video call :)
Google message platform? better avoid it because in a bit it will be 'phased out' to make room for two new ones... never again another Google service!