Breaking into the enterprise market has it's own difficulties as I am sure you are already aware of. Having been directly and indirectly involved in several large IT software purchases I can tell you that more often than not, large purchases/contracts are not made based on features and/or price. They are made 3 levels above you by personal relationships.
That is why you have huge IT shops wasting countless hours dealing with clearcase UCM inadequacies when there are comparable and even better options available for free or cheap.
At the time of purchase the argument given is that the staff required to administer the free software will cost more than the license and support contract but in the end you still end up hiring a full time staff of 14 to manage that clearcase system and blame issues on the hardware.
In the case you can break through the gold-ol-boy sales process with your revolutionary product the cycle for a product costing as little as 20k can be upwards of 18 months and if it is terminated at the zero hour you have literally wasted hundred of man hours chasing a deal that you will not be getting paid for.
To answer the original question, If I where to take on oracle or attempt to make them irrelevant I would be Atlassian software (JIRA/Confluence/etc.). While they are not offering competing products to oracle or IBM they do have the ability to work from the developer upwards to find there way into even the largest enterprises.