Not necessarily. It's not like IBM doesn't sell x86 processor systems along with their POWER (and Cell?) processor systems.
Oracle will probably package their own hardware by leveraging Sun's resources. You will probably be able to purchase a Sun-Oracle SPARC system and have a choice of Solaris or Linux (which also runs on SPARC) to run your Oracle database on. Otherwise you can run Oracle on Linux if you aren't buying into their integrated hardware solutions. I don't see how they would have to drop everything without being able to make it work together.