I have seen that topic where you answer about the same question.
But it was 1 year ago.
Today I can see this in HyperDB FAQ:
How does HyperDB support partitioning?
HyperDB allows tables to be placed in arbitrary databases. It can use callbacks you write to compute the appropriate database for a given query. Thus you can partition your site's data according to your own scheme and configure HyperDB accordingly.
Does it mean that I can now do the same with HyperDB - eg to have multiple databases and to distribute tables between them based on blog ID?