We're at an embryonic stage with a big BI project really, and are planning on re-working all our internally developed web applications utilising SharePoint (especially SharePoint workflow designer for case management).
Since you say "big BI project" does that mean you are going to be on Enterprise Edition? If so then if you make a true EDW the significant enhancements to column store indexes, more online operations, improved optimizer engine, better partitioning, etc could be worth the wait.
If you aren't doing Enterprise Edition I don't think I would wait (and incur the non-zero risk of using 2014 soon after release).
Kevin G. Boles
SQL Server Consultant
SQL MVP 2007-2012
TheSQLGuru at GMail