Sorry for the mocking tone -- I edited my original comment. It's easy to forget people are in very different environments and that affects our perspective.
If you're still thinking of gchat as a desktop AOL Instant Messenger replacement then I can see that products that seem to operate that way are disappearing. The way people are using chat products is changing drastically due to mobile. I would say AOL-style chat isn't going away because Google killed the competition -- rather I think demand for those style systems is just dwindling in favor of multi-platform, multi-modality, multi-party chat clients (picture/text/video, desktop/tablet/mobile).
Ha. I can see your environmental bias: AIM? AIM in Europe came late and never really took off. Here the first popular IM was ICQ, then MSN, Yahoo and local projects (c6, gg etc), then Skype, then WhatsApp/FB/Hangouts etc.
I agree that classic desktop IM apps have changed anyway, except in the enterprise world (where MS and IBM still ship horrible, horrible stuff).
If you're still thinking of gchat as a desktop AOL Instant Messenger replacement then I can see that products that seem to operate that way are disappearing. The way people are using chat products is changing drastically due to mobile. I would say AOL-style chat isn't going away because Google killed the competition -- rather I think demand for those style systems is just dwindling in favor of multi-platform, multi-modality, multi-party chat clients (picture/text/video, desktop/tablet/mobile).