If you think your project is going to need more than the 64K of code & 64K of XDATA directly-accessible by the 8052, I think you should seriously consider whether it is the right chip for the job.
Sure, you can do both code & XDATA banking - but it will greatly complicate both your hardware & software design & debugging.

There are various 8052 variants which support larger address busses - Erik has already mentioned the Philips MX.

The Triscend E5 has a 32-bit external address bus, although its 8032 core can still "see" only 64K of code & 64K of XDATA at a time. The E5 relieves you of the hardware design to support large memories, but you still have to provide the software support to use its address mappers...

The Keil tools support both code & XDATA banking, and various other cunning tricks to maximise your memory usage - have a read of the manual (full PDF manuals are included in the free download & CD)