According to Facebook, more than 680 million of its one billion users now check the social network from mobile devices.
Ernest Doku, telecoms expert at comparison site uSwitch.com, said the arrival of a 'Facebook phone' would mark a new departure for mobile devices.
"After a protracted journey to market, the 'Facebook phone' finally seems set to arrive," he said.
"The device is a concerted bid for Facebook to make a play for the eyeballs of millions of consumers, and become the hub from which they interact with all aspects of their smartphone.
"The important word on Facebook's invitation is 'home'. We should expect Facebook to greet mobile users when they turn their smartphones on in the morning, and to be the core of the user's experience - integral to searching, surfing and interacting."
He added: "This forthcoming device will be the tip of the spear - a focused showcase of what is possible with deeper Facebook integration - and is certain to mark the start of future devices which embed the social network into the fabric of functionality, from a number of manufacturers."
Both Facebook and HTC have refused to comment on the speculation surrounding the announcement.
Stuart Miles, founder of technology and gadget site Pocket-lint, says he thinks the Facebook announcement will be the launch of an enhanced app for the social network.
My initial thought was that they couldn't possibly be launching a phone because that would be silly, because every phone is already a Facebook phone.
I think ultimately this will be an enhanced app that you can run from your homescreen on Android which will give you the feeling that your phone is a Facebook phone.
– Stuart Miles
The launch of an "enhanced app" would reinforce Facebook's "mobile first" attitude, Miles added, as users increasingly monitor the social networking site from smartphones and tablets, rather than desktop computers.
Facebook will reveal its "new home on Android" today at an event where the American company is widely expected to unveil a homescreen for smartphones.
The social media giant has refused to divulge any further details relating to the launch beyond promising a "product announcement". An invitation asks guests to "come see our new home on Android" at a function in California.
The event has already generated widespread interest online, where much speculation surrounds the rumoured Facebook homescreen which analysts suggest would run on Google's mobile operating system Android.
TechCrunch predicts the new product will allow news from Facebook to be piped automatically to locked Android homescreens.
Meanwhile VentureBeat reports leaked information suggests the HTC-built Facebook phone is now a reality and has been dubbed the HTC Myst.
Andy Rubin, chief executive of Google's Android, the world's top-selling mobile operating system, has decided to step down as Google combines mobile software divisions under one roof, the company said.
Google appointed Sundar Pichai, the executive overseeing its Chrome web browser and applications like Google Drive and Gmail, to take over Rubin's responsibilities, hinting at how the company with the dominant Internet search engine intends to address the rise of mobile devices.
In a blog post, Larry Page, Google's chief executive and co-founder, credited Rubin for evangelizing Android several years ago and building it into a free, open-source platform that runs on nearly three-quarters of the world's smartphones.