I cant recall a single UI library / framework (with the solely exception of Jquery) to be mantained that much. In less than 5 years VR, AR will probably be mainstream, and UI technologies will probably to be revisited from ground up again.

Can you trust the web as we know it to exist in 10+ years?

short answer: "No".

Explanation: In js land, Long term Support means "6 months". so your best bet is to have a framework which makes migrations easy and does not introduce changes.

With angular being backed by google, there is no guarantee if angular will be maintained 4 years down the line.

PS: feel free to keep your million dollar.

Angular 1.x has been around since 2009 - 7 years - that predates pretty much every framework in use today, before modules (commonJS, let alone ES6) were widely in use, etc. At some point, we had to make a decision to be forward looking towards the future of the language. Support for 1.x won't disappear for some time. Angular 1.5 had a number of big upgrades - a focus will be easing the transition to 2.x over time ( .component(), lifecycle hooks, etc...)

I think there is another problem. With framework the size of of angular is hard to maintain. It will be hard for others to take over if needed. With react's smaller parts every part (redux, react-router, etc) can be maintained by a small group of people. If some part isn't maintained anymore you can switch out that part. With angular you might have to rewrite the whole application. That is a risk I would like to avoid.

It is easy to expect that during 10 years, at some point this application might get completely rewritten...so not that important either, if we are talking about the framework longevity...