When you look at the bottlenecks in opcode throughput for virtual machines it's almost always lousy branch prediction. Using a branch table instead of a switch block is not going to make much of a difference in any realistic program. The CPU has no idea which function is going to get called next so it can never fully use all the advanced look-ahead mechanisms.

For those interested, look at all the performance improvements made in the ocaml and perl and clisp interpreters. There is a lot of low hanging performance fruit left in the Python interpreter - the question is whether it's worth plucking. For instance, python can get a dedicated accumulator (I don't think it has one now) and you can introduce new opcodes that combine functionality of frequently occurring opcode sequences. For instance, python now has a LOAD_CONST and BINARY_ADD instruction, but not LOAD_COST&ADD instruction like clisp.

By combining the functionality of two instructions into one you're essentially saving an opcode dispatch. Saving a jump is going to make a bigger difference than making a jump faster. So that's where I think the python guys should focus on if they really want to improve performance.