Well, tables wonʼt be part of the v1.0 core specification, but it should probably take care of special rules for the pipe character | already: CM-based GHFM requires it to be backslash-escaped even inside code spans in tables.
As soon as we have agreed upon a common way to document extensions, people should start to write specifications for their pet features which are at least as detailed as the core specification, so @jgm does not have to take care of everything.