Does SAP HANA gradually phase out SAP BI

1. Can HANA store all the data carried by SAP BI in HANA "in-memory"?
2. Are there certain BI tools that are available only in SAP BI and not possible in SAP HANA due to architectural differences in nature of Data warehouse and Database tools now and in future? If yes, what are those?
3. How does a SAP BI developer use HANA? Does he write HANA SQL Scripts on SAP BI along with ABAP code for BI customization?

ad 1) Yes it can, but it doesn't have to (dynamic tiering and memory displacement can be used).

ad 2) Datawarehouses and DBMS are two different things, so there are lots of differences. If your question is more directed at whether or not SAP HANA can and will replace SAP BW anytime soon, I recommend the following blog posts:

• https://blogs.saphana.com/2012/06/13/does-sap-hana-replace-bw-hint-no/
• https://blogs.saphana.com/2012/06/20/does-sap-hana-replace-bw-hint-no-part-2/
• https://blogs.saphana.com/2014/04/17/does-sap-hana-replace-bw-hint-still-no/
• https://blogs.saphana.com/2015/07/06/sap-hana-replace-bw-hint-no/

ad 3) Yes, that's the case. For example expert routines can often be scripted in SQLScript, thereby avoiding data transfer between HANA server and SAP BW application server.