My advice to you is invest cautiously in this industry. As you know the trends in the IT industry is moving at an unbelievable fast pace. Organisations are beginning to allow their employees to bring in their smartphones and tablets into the workplace. Some have even gone further by allowing their employees to view corporate data on their personal devices. This along with corporate data in the cloud should begin to answer the question where your money should be going. Other than this, unless your investment has a big marketing machine behind it the risk of seeing a profitable return on your investment begins to wane.
All Enterprise DRM products have limiting features that give its customers a complete satisfaction. For example I am currently working on a project that is cloud based solution but only works with one web browser and not the others, this can always lead to frustration for the client, resulting in canning the whole idea altogether.
The market opportunity is still highly untapped especially in the Apple iPhone and iPad space, Android, Windows Phone, Blackberry (currently in decline, but still big in many parts of the developing world) and other personal electronic devices. There is also the Cloud, in other words you develop solutions that will make access to confidential data stored in the cloud seamless, but the true secret to such a solution is making it seamless in terms of access to all mobile and desktop operating systems.
Regarding potential customers, I would say from a corporate perspective banks, pharmaceuticals, legal firms, publishing, oil and gas, and manufacturing are your main targets. On the whole anyone who needs to control how sensitive and confidential information is distributed. Symantec and Adobe are great products, but have very limiting capabilities and are not the market leaders in Enterprise DRM, but as I said previously there is scope for growth. I hope I have answered all your questions.