You're absolutely right. If you're a SaaS developer you're going to build your application for the most widely distributed platform that meets your needs so that it is as easy to sell as possible. However you're overlooking the possibility of new functionality made possible by HTML5 (and other open standards) which could enable the development of SaaS apps that address specific needs of the enterprise that were not previously possible without a client application. Look at some of the stuff Google is exploring with their upcoming extension store thing for Chrome. Those applications may not exist yet in widespread use, but that's not the point. The point is that they are now becoming possible, and possible only on the platforms that support the new technologies. If those platforms are in widespread enough use at this point to justify development, and if the use cases are compelling enough to some buyers to justify installing a browser (where they would have previously installed a client app, which is just as expensive if not even more expensive to maintain) then the tide will really start to shift.