Apple's UK Store leaks some information which suggests that
8-Core Mac Pros are coming soon.
When searching for "Mac" in the UK Apple Store, the listing for the
Mac Pro is:
Mac Pro
Now quad-core or 8-core
processing power.
Configure yours today.
Rumors that Apple would incorporate two of Intel's Quad-core chips
into a Mac Pro to produce an 8-core Mac Pro have been ongoing since
late last year.
Latest Update: Apple appears to have found it and
have removed the text from their site.
Source