What are some of the hottest SAP domains to nowadays start a consultancy practice in?

I would say that technology-wise (with corresponding links): 1. Mobile (http://developers.sap.com/mobile) 2. Database technologies (http://developers.sap.com/hana) 3. Cloud-based development (http://developers.sap.com/cloud) But industry-specific expertise is even more valuable than technology nowadays.

Is rather interesting that most answers, except for Vitaly, focus on the technology side and do not mention that industry expertise is important. It really depends what you want to achieve but I would say that you should, before deciding the technology to use/focus on, listen to your customers (or potential/future customers). Most customers that I know don't chose their SAP integrators by looking into the technology side but more by evaluating their experience on the industry. The way a company works in the Utilities sector is not the same as a company that is on the Fast Moving Consumer Goods industry. You should first understand which industry/industries you can help, listen to your customers/future customers and then chose the technology to use. SAP evolves, the industry/industries evolve but the industry/industries will still be around and in business with or without SAP software.

I agree with Vitaliy. Best opportunities are in niche markets. I would add as fourth element to the list Solution Manager. Even though it has been used for a while now, SAP is reinforcing it's strategy for Solution Manager and demanding it's use from customers.

SAP HANA - BW is already moved to HANA. It just a matter of time before the whole SAP ECC, CRM, SRM , etc moves from oracle based DB to HANA. It it super fast and it compatible with lots of suffs eg : with Hadoop using Smart Data acess, Mobile , etc.

Mobility, HANA, performance optimization and hybrid architecture.