If you have not heard about the new project of Sap,Hana - High-Performance Analytic Appliance - a project which should bring the best of bread in terms of performance.
I think that there is no doubt that the future of BI has to grow through the in memory capabilities
and SAP is getting us close to that place.
Here is a quick review written about HANA in the http://biscorecard.typepad.com/biscorecard/ :
"Queries that the customer used to run in two to three hours now run in two to three seconds. The data volumes were not that big – 9 million customer records. But it’s the complexity of customer segmentation and that the queries were running directly in the transactional source system that made for the slow queries. Christian Ritter, head of Reporting and Global IT at Hilti, explained that with HANA, they would skip building a data warehouse altogether. Data is replicated in near real time from the SAP transaction systems into HANA."