You have options
Sun's direction into x64 is clearly an indication of where the market is heading. There are many companies willing to assist with a SPARC to x64 migration to Linux or Solaris x64. Take Transitive. You can use Transitive's QuickTransit product to quickly migrate SPARC applications onto x64 servers immediately saving support.
Also those of you languishing on SPARC T series servers check out what Azul system appliances can do for your app tier.
I am partial to HP ProLiant servers which provide Windows, Linux and Solaris x64 support. HP provides more flexibility and more choice at much lower costs with none of the roadmap risk I see with Sun.