All these developments are happening among browsers which have a combined market share equivalent to one fourth to one fifth of the one engine enjoyed by IE, the leader (in browser market share) offered by Microsoft. However, they point to an interesting scenario about how new features go from being enjoyed by a small but vocal minority to a wider audience. Tabbed browsing was one of the big innovations that Opera introduced in the marketplace but it wasn’t until Mozilla’s implementation that it started getting noticed. Once developers got used to it, they realized that it was difficult to use browsers that did not offer it and “demanded” that the feature be available in any new browser.
This is an area where an open source project like Mozilla can be considered to have contributed to the mainstream. While Mozilla’s market share remains tiny in comparison to that of Internet Explorer, its impact on web browser development is growing. On one side, it is helping improve the way web pages are developed (due to its strong support for web standards), and on the other, the joint effort of thousands of people are helping develop features that match or improve on what is offered by other browsers.
Since the popularity spurt of tabbed browsing, there hasn’t been any major development coming from the Microsoft end (most of the focus has been in fixing a number of annoying security bugs in their browser) but I would expect the feature to show up in future versions, as IE is now the only browser not to sport the feature.