As a vendor of mobile enabling technology for ECMs we are integrating with a large set of solutions and follow the ECM and DMS market development closely. There are definitely pros and cons with On-Premise vs. On-Demand and only knowing your specific requirements, you will be able to settle for one of the two.
On-Demand is where we see a lot of traction right now where end users want to reduce cost and invest by going to the cloud. Major issue for larger enterprises is that they cannot utilize On-Demand services not being physically located within their own national borders, e.g. you will never get a Swiss bank or a French insurance corporation to host their data in the US or in an unknown cloud location. For smaller corporations or corps with more lax security this works easier. The On-Demand providers belong over-all to the most agile of providers and are looking at both further "verticalizing" their offering (going legal and compliance, HR-this or that) and to broaden their services.
The "old time" vendors are all pushing their cloud service offerings and the global system integrators have all their cloud strategies in place, no matter if they are truly solid offerings or rather shaky. So, all are pushing towards On-Demand and, then of course you can also run Sharepoint on e.g. Azure.
On-Premise becomes a must requirement as soon as you are not willing or able to use a cloud offering at an unknown location, or at least your service provider must be able to offer you a nationally hosted service.
Multiple vendor strategies is a reality in probably all major corporations. You will have multiple, different systems from different vendors. Sharepoint may play a role on the department level and be competing with large ECMs that are rolled out on a corp wide scale. We are seeing a mix of On-Premise and cloud here as well, where certain data can be placed On-Demand whereas other type of information is kept inhouse.
Our bet is to "integrate it all", e.g. you can use multiple profiles from the same device or client to access stuff located both on your ShP, ECM1 and ECM2, which might be SaaS and On-Premise. Knowing that the world is not going to be any easier any time soon we believe such a multiple vendor, multiple support strategy is a sound move.
More to come.