The OP hypothesized merger between IBM and Sun would have been better than Oracle/Sun. If IBM had bought Sun, they would probably have killed the SPARC because IBM has their own RISC CPU, the Power series.
IBM maintain their mainframe business. While nobody's writing new applications for ZSeries, much like SPARC, there are some very profitable, untouched apps that run on Solaris 8/SPARC and they'll be around till the company gets the time and budget to port them.
Brian Aker says "I'm sure everything else Sun owned looked nice and scrumptious, but Oracle bought Sun for the hardware." http://radar.oreilly.com/2010/04/a-mysql-update-from-brian-a... which means the SPARC survives.
[edit: proper quote]