Let me start with a couple of common generalisations:
- SOA is Enterprise
- Enterprise implies big and good
- Desktop means small scale, possibly old fashioned and not so good
Now you may quickly dispute those crude statements but I would guess that they will have a slight resonance for you or at the very minimum you will know several people who hold views somewhere close to them.
At GDC we were very committed to delivering more and more in a browser based interface. For a while we talked to clients about funding the cost of a web solution through reduced deployment of desktop software. Well a few years on we have not seen the predicted decline of desktop, in fact the sales of desktop continue to grow and those clients who thought they were going to reduce the number of desktop users keep finding new tasks.
Over the last couple of years MapInfo Professional (and most other mainstream desktop GIS products) have incorporated support for both OGC web services and some SOA offerings, in our case Envinsa On Line Services. The power of combining desktop tools with enterprise web services opens up a whole new range of possibilities particularly for the delivery of data rich capabilities such as geocoding or drivetime analysis.
As more and more capabilities are exposed as services so the opportunity to craft these services into custom workflows with desktop products will become the norm. Browser based applications are great for known workflows but the power of the desktop will be in the unknown, the ad hoc requirement.