The combination of Gmail and Google Drive will not put Microsoft's Outlook application out of business. Outlook it too in grained in the Microsoft's Office suite, including the online verison to be overtake by any third-party application. The Gmail - Google Drive option will and is seeing strong growth in the mobile market.
No, Gmail and Google Drive will not put Outlook out of business. Although these applications will undoubtedly take some business away from Outlook, they will not impact it so negatively that it will go out of business. Outlook is the standard for many large businesses and they will not be likely to change to the Gmail platform any time soon. Some businesses and users may make the switch, but not enough to make them the industry standard.
Outlook might not be the most popular place to get your mail and use for online activities, but the big company isn't going anywhere soon. Gmail and Google Drive have dented the allegiance of Outlook, but people who have used the services for years have no intentions of going anywhere soon.
Outlook has great e-mail, and a lot of people still don't use GMail. Outlook has an easy, streamlined look and great spam defense. I also don't think that everyone really knows what GMail is yet. There is something for everyone. In addition, a lot of people do not know what "the cloud" is.