OMS: Broken business models

The march of SaaS is pretty relentless in the buy-side enterprise software market but it leaves an unanswered question..

Can buy-side OMS vendors actually "eat-their-own-dogfood" and manage their system over their entire client base?

One of the rarely spoken truths of the OMS market has been that the economic models of the vendors were based upon generating more and more new licenses (and associated implementation professional services) as the recurrent revenue from the existing client base was not enough to keep the business operating.  This constant desire for increased revenue has brought about pretty conflicted business models where for example, at least one OMS vendor receives a large payment every year from a connectivity provider to which the OMS pushes clients.  This is not disclosed in a transparent manner...

Once the OMS vendors have to simply earn recurrent revenue on a monthly per-user per-module SaaS model will they thrive or wither on the vine?  Will open source such as Marketcetera with the great taste of free and open source start to gain real traction in a cost-constrained real-money buy-side world?

Interesting times as consolidation in this space interacts with cost pressures and a drive to operational excellence and SaaS.