This San Francisco Chronicle article gives some clues as to who 2007 interleague opponents will be -- the NL West plays the AL East.
USA Today Sports Weekly reports that in addition to that, the NL East will play the AL Central, and the NL Central will play the AL West.
The Cubs have played AL West teams twice -- in 2002, the Cubs visited Seattle and hosted Texas. In 2004, they went to Anaheim and Oakland came to Wrigley Field.
If this is indeed the case, the Cubs will likely play only 12 interleague games next year -- since the AL West has only four teams -- the two series with the White Sox, and my best guess, the reverse pattern from 2002; thus, the Cubs will go to Arlington, Texas, and Seattle -- and Ichiro -- will come to Wrigley Field.
Stay tuned for more schedule info as I get it.