IF you are willing to spend some SERIOUS money, you can replicate from Sybase to SQL Server. It will almost certainly be cheaper to just buy SQL Server, and set up the replication that way. If you are really looking for some pain, you could try to set up PowerBuilder PipeLine objects.
The question boils down to:
If you have practically unlimited development time, you can keep the present implementation and write PipeLine objects.
If you have practically unlimited money, you can buy Sybase Replication.
If you have limits on either your time or money, buy Microsoft SQL Server.