It's highly unlikely in the near term. The software my firm uses is Autodesk Revit's "Building Information Modeling", a highly evolved "intelligent" 3d modeling database system. The software uses every byte of ram, every hz of cpu, every byte & hertz of video interface on a users system - it takes serious horsepower to run a large model which is accessed over the network by multiple users. (Refreshing the model remotely via vpn over dsl can take 15 minutes) I don't see AJAX coming close to handling this kind of load for a long while. Also, the files can be huge, and in a web-hosted environment, the file storage would have to be absolutely massive and absolutely fast.
An interesting note is that Autodesk started out with Autocad, which they coded in lisp (eventually transformed into autolisp.) They took the MS model to software development and proceeded to make bigger and more complex versions with increasing quantities of bugs to the extent that multiple crashes per day were the norm. But they owned 80% of the world cad market, they became the 2nd largest software company in the world.
Revit was developed by a small company with an incredibly sound software architecture with a database at the core(without the massive bandaids that had piled up in Autocad and are still there today.) and developed a devoted cult following. Autodesk fought back with "Architectural Desktop", which I bought (before I knew about Revit). Their version: Cut a section through a building, wait 30 minutes. Revit, Cut a section through a building - instantly. Autodesk got very scared, then bought Revit. They saw the writing on the wall and undersood that Revit would be completely replacing Autocad in the next few years, which it is doing now.
So if MS can buy Google, they'll be all set :)