Those are (closed-source) products though - Go and Dart are languages, and both are open source to boot - so if Google drops support, the open source community - and definitely the larger users that depend on it - can take over without a hitch.
Google Code is being dropped because nobody uses it anymore. Google Glass is on hold because nobody wants to use it and it's not ready yet. Google Video was dropped because they bought Youtube after realising they couldn't compete with them. Google Reader... I don't know, that was a bad decision on their part. Google+ was their biggest failure to date, I think, not because of a lack of effort on their part but because it never got the traction they wanted it to get.
Same as Google Wave really - too early, or nobody needed it, or something like that. At least they open sourced that project.
I think most if not all of the core team for Go are employed by Google, so if Google dropped Go it would have a huge impact. The community could pick it up but let's be honest, without the original backing by Google, the language would never have gained traction and would be just one of many interesting languages.
All those projects it dropped were consumer facing. These are programing languages being used inside google to increase productivity making a comparison between the two is a straw mans argument.
Google Code is being dropped because nobody uses it anymore. Google Glass is on hold because nobody wants to use it and it's not ready yet. Google Video was dropped because they bought Youtube after realising they couldn't compete with them. Google Reader... I don't know, that was a bad decision on their part. Google+ was their biggest failure to date, I think, not because of a lack of effort on their part but because it never got the traction they wanted it to get.
Same as Google Wave really - too early, or nobody needed it, or something like that. At least they open sourced that project.