I heard this rumor at the Portland CMG meeting yesterday. Apparently, Sun has been quietly "looking for a date" for some time. Presumably, IBM's main interest is in Java IP. Will Solaris replace AIX (under the covers)?
"Shares of Sun Microsystems, which makes the Java software that runs many Internet applications, were up 78.9 percent after reports that it was in talks to be acquired by I.B.M. Shares of Sun ended at $8.89. I.B.M. was down 1 percent, to $91.95."
I had a long-standing theory that Sun Microsystems would be bought by Fujitsu Corp to simply milk Solaris service contracts for the next 10 years. It's not interesting innovation, but it is a business. Sun has always managed to have enough cash in the bank to be able to forestall such a move, but now, they're out of gas.
Update: Why an IBM purchase of Sun would make sense (cnet)