Netflix will have the most competitively difficult path forward, with massive and aggressive competitors swarming in from all sides. You've got the recently-awoken content giants (Disney+, Paramount+, HBO Max, Hulu, etc), and then you've got new players like Apple and Amazon with deep, deep pockets.
Google can take a lot of criticism for being relatively complacent and without much visible innovation lately, but they'll coast on Google Workspaces (G Suite), search/advertising, and their OS marketshare just like Microsoft did for decades. They have ample time to make and correct mistakes. I've also noticed that whatever products their intense focus is on often see rapid, high quality improvements (like when Google Meet development accelerated after the pandemic started).
Facebook could go either way. It owns Instagram, of course, and I think they know the social media business well. WhatsApp will never go anywhere, it's entrenched. They're big enough to copy novel new social media ideas quickly. A highlight is that they truly are a leader in VR, and the Oculus Quest is clearly a hit in that category. If VR and AR truly become big businesses (skeptical on that but we'll see), Facebook will be growing.
I can't see Amazon declining due to their dominance as a logistics company for everything. They can become truly awful any everyone will just keep using Amazon.com and AWS.
I don't know if this is a bold prediction, a safe prediction, or just one that will get me accused of being a fanboy, but in this list think Apple is the least likely player to decline in the years ahead. They have shown time and time again that they have good management in place that has a long-term vision in mind. A lot of people say that Steve Jobs was the greatest and Apple isn't the same anymore, but they've taken advantage of every possible high margin business with their newest products in the post-Steve Jobs era. Apple Watch with its accessory ecosystem (like $400 Hermes watch bands), headphones and audio, and all the subscription services.