No one can really tell you this as it depends on future events. will web assembly stay supported, will web applications stay a preferred ui, etc.
on the plus, blazor unlike silverlight is hosted by a web standard (web assembly). yet while web assembly has been declared the future of the web, blazor is probably the most popular toolkit.
the reality is that the web application development is a fast moving technology. you would hard pressed to pick any framework guaranteed to last. what ever you pick today, may or may not look so good 5 years from now. You need a plan to stay current. You should reevaluate your decisions on a regular basis.
Thank you for the link, but that is the development team's expected roadmap. This is not any sort of LTS commitment from Microsoft, who could decide to scrap it regardless of the team's plans.