As you have not started your build, I would suggest going straight to SQL 2014.

You will have read about the in-memory and column-store stuff, and they will help BI just as much as OLTP, the only pain is they are Enterprise Edition features. SQL 2014 also has other improvements such as improvements to the query optimiser that everyone benefits from, regardless of use of the other features. IMHO SQL 2014 Enterprise Edition gives enough to make the upgrade almost a no-brainer if you already run Enterprise Edition workloads.

I do not know when SQL 2014 will be released, but I have read two publicly available things that make me think it will be Q1 2014, maybe even January...

a) Upgrade to SQL 2014 RTM from SQL 2014 CTP2 is supported - my view is this means there is not a lot of new stuff coming.

b) SQL 2012 CTP2 expires on 31 March 2014 - my view is that with a CTP3 being very unlikely (due to lack of new features) then the RTM date has to be at least a month before CTP2 expires so that people have time to upgrade to RTM.