Does Outlook.com have the potential to attract more users than Gmail.com?As many said, Gmail was the most disruptive innovation Google made. Do you remember mails before Gmail? You had 2MB space, you could create folders to put your most important mail in and.. almost all. You have to empty your mailbox and trash often unless your account is full. Google created a huge disruption proposion 7GB boxes, labels to recognize your emails, mail reading offline even in the browser, very usefull filters to automatically manage your emails, chatting directly when typing emails, a very unique user experience never got before.. and now integrating Google+ in it: such a very unique UX had never got elsewhere since then An other thing: professional mails can also benefite from gmail technology. And last but not least: Google is trying to move this UX to mobile by buying Sparrow start-up.
To do such an enormous leap, Google made its own servers and network infrastructure, the way it is managing Google Fiber service right now. Google invested so much ressources in email.
Well, you know as first mover, Google has a huge advantage. Other competitors try just to look like Gmail, but never can be as interesting, as Gmail it self is getting improved continuesly. So really don't think there will be something similar elsewhere. This is why I think that Gmail users number will continu growing faster than other competitors.
The thing is that user behavior is changing, and we are communicating less and less by email since social medias dominate. Probably will Google dominate mail service in some years but it had yet to reinvent email usage again.
This question reveals the biases formed by Quora audience, as compared to the Internet as a whole. Why? Because Hotmail still has more users than Gmail, so Outlook.com will "get" more users if Microsoft just forces all Hotmail users to use it's (much better) site instead of the existing Hotmail site. Quoting from a David Pogue post today on the New York times, "Hotmail is still the world's largest e-mail service, with 324 million members. But Gmail, only six years old, already has 278 million".
If the question is instead "Will 300 million NEW Outlook accounts get created?" -- highly unlikely in the next, say, three years. Email creates huge platform lock-in, and huge switching costs, even though Outlook.com can be used as a backend for an existing Gmail account address.