Dart/flutter sound good and I have heard good things. The downside is you’re rolling the dice on whether it will still exist in five years because it’s a Google project.

It’s open source, so it will likely exist in some form.

GWT still exists and had a release last year. It’s been 9 years since it fully transitioned to an open source project. I’m not sure at what point Google stopped contributing since I see old team members in the commit history.

A lot of companies would be really upset at Google if this happened.

Besides Google, who re-wrote several of their own apps with Flutter, like Pay and their Home devices (which some are apparently running fuchsia now?), there's BMW, eBay, STAIR (US Department of Veteran Affairs), Nubank, and plenty more.

> A lot of companies would be really upset at Google if this happened

There's lot of projects that Google has killed for which this is the case, though. Stadia had people building for it, and Reader had people building atop it to name maybe the two highest profile ones. Of course, the cost vs value of maintaining those for Google was a very different question, but on its own, other companies' interests don't seem to move the needle much for Google when it comes time to kill a project.