James Fee has an interesting post on "The Day ArcIMS Died", talking about the impact of Arc2Earth Publisher. I think that aside from the obvious impacts that Google and Microsoft are having on the geospatial industry, a more subtle one is that they are helping to crack the unswerving devotion that most traditional GIS users have generally had to their selected vendor.
Google and Microsoft have such a high profile that it is hard for even the most insular organizations to ignore what they are doing. My hope for the industry is that this will help open people's eyes to the fact that there may well be better solutions out there than their current vendor provides, not just from Google and Microsoft but also from other companies or open source initiatives, so I think we will start to see more organizations selecting software based on its merits, rather than just choosing their incumbent vendor without doing any real evaluation. There was another interesting debate on James' blog a little while ago on the topic of "Are we begining to see a shift away from ESRI Server backend to Open Source solutions?", and one of the comments there said "I work for a US government agency that is getting ready to send out a RFP for GIS servers that has no ESRI requirement. A first for us". This type of increased competition will only be good for end users.
I think that traditional geospatial vendors who do not embrace and leverage what Google and Microsoft are doing, but try to fight them, are fighting a losing battle. Heterogeneous geospatial systems will be much more common than they have in the past.