I don't believe thats there are any statistics about the usage from SAP BI tools against other SAP frontends. Many companies which use SAP since years have invested a lot of time and money to implement a SAP BW / BO environment and many of them won't be rethink these decision although there are not really happy with them.
I suggest your company makes a SIB with your SAP people and one with an experienced QV partner - especially to the topics of development times, costs, flexibility and response times - and don't believe that altogether the SAP BI tools will be a better solution as QV with his connectors.
I think you will find here more informations:
and a visit to a qlik conference, qlik talk or similar could be helpful, too:
I´m a SAP BI Consultant, that work with Qlikview too.
I can tell you that, in my experience, Qlikview is more powerful, simple, on give a better experience to the user.
SAP BW is a very good Data Warehouse, but the tools for visualize data, are not strong enough to compete against Qlikview.
BO is a well data visualization tool, but Qlikview is better.
And SAP Lumira is still too new to compete against Qlikview.
In my recommendation, is a good idea combine SAP BW with Qlikview.
In the only case y could say SAP surpass Qlikview is with SAP HANA.