Drivers of Google's Future Revenue Growth

What major factors will influence the future growth of Google's revenues?

• Growth of the advertising market
• Increased share of online advertising as part of the overall advertising market
• [Extension of Google's business into offline advertising]
  
• Increased share of search-based advertising as part of online advertising
• [Extension of Google's business into non-search-based online advertising]
• Increase in Google's share of online searches
• Increase in Google's ability to monetize online searches relative to its competitors
• [Extension of Google's business into non-advertising businesses]

Any of these drivers can be considered, say, by country or by industry.