SPA is a new useless buzzword for technic already existed for many years and called DHTML.
It is true that most of modern apps are very dynamic (D in DHTML): they use AJAX, APIs, animations, dynamic content/page loading all the time. SPA just replaced old DHTML term. So somehow it is possible to say that many apps today are SPAs.
In reality, it is a wrong statement. App can't be an SPA. Let me explain what a SPA really is: SPA is a very complicated and dymanic page, only one page within your app, but it's never a whole app. News feed (Index page) in Facebook is a classic example of a very complicated SPA, however, many other pages on Facebook are still simple PHP pages and actually some pages like help, docs are static HTML pages.
Don't listen to the quantity, listen to quality and always think yourself. Many people just don't want to think and because of that the most of the information you read on the Internet is a garbage.
Is SPA a future? No, it can't just because It is a technic from the past. Check, for example, how YouTube or GitHub loads some of their pages/sections, it is just oldschool AJAX which receives ready HTML from the server and just inserts it. Even URLs changed at that time with #! but now we have a modern Browser History API to make friendly URLs even from JS.
The main problem with SPAs and Angulars is - people just don't want to learn or keeps ignoring the simpleness of HTTP itself - the core of the Web. Sir Tim Berners-Lee invented a very simple mechanism of building documents for the Web and transfering those documents from one PC to another. Modern Internet is 25 years old now and this mechanism is still the most simple for that job - connecting the information on the Internet and it is still used billions of times every hour. You can't use something else here. There is no need of overengineering and overcomplicating things. If people want to build web apps like native apps they, probably, need to invent other protocols first, but I'm sure these attempts in Web will fail because HTTP and HTML is and will be the simpliest way for sharing the information globally.
The fastest apps are not SPAs with 2MB of JS, over 9000 loaded scripts, styles, content via AJAX all the time. Fastest apps are oldscrool static server generated HTML via PHP, Python, whatever else with bundled, minified, gzipped one CSS file and one JS file, may be one SVG file. In some cases it can be inlined into first page. Server should return only the minimum-maximum of what IS needed for current request, no more - no less. Wisely combining this HTML with simple JS, AJAX and JSON will give you power to build modern and fast apps. Web Standards are evolving and today there is a preloading specification which will improve the perfomance of modern apps.
SPA as a term and Angulars will be forgotten in few years, but the creation of Sir Tim Berners-Lee will be remembered in the history of humanity forever.