Hi Jeff,
You are right - a lot of considerations are taken into account when deciding to merge BPC and BW boxes or keep them separate in 10.0.
Some of those are:
1. How much data is coming from BW and how much from other sources?
2. What is the effort of regression testing of BPC when BW needs and upgrade or HANA needs and upgrade for BW reasons?
3. What is the effort of regression testing of BW when BPC needs BW upgrade or HANA needs an upgrade for BPC reasons?
etc.
In 10.1 most of those questions are still valid for Standard mode, but some aren't anymore be for Embedded mode.
Since BPC is very fast evolving product I wouldn't recommend to look at 5 year horizon - in 5 years today's reasons could be not valid any longer. Just try to make sure that in 1-2 years you don't have to redesign everything.
Regards,
Gersh