"I think one interesting project in the near future could be to try and build a column-oriented storage engine that's "good enough" for both OLAP and OLTP workloads."
SAP Hana is an example of a system that fits into this category. This isn't new either and has been existing since the 90s.
Sybase IQ (which SAP acquired) was the first commercially successful columnar database. They have an in-memory row engine to handle OLTP. OLAP queries perform exceptionally well due to the column oriented nature of the storage. Customer deployments are in the 100s of TBs and low PBs these days. Blows most open source software in terms of performance if you are willing to shell out the $.
Source: I work at SAP.