Processor

Phoebe will initially be supplied with a 233MHz SA-110 StrongARM processor, mounted on a small daughter card.
Dave Walker firmly stated that faster StrongARMs are in the pipeline; however, he would not be drawn further, citing Non-Disclosure Agreements with Digital.
Acorn do intend to provide new processor cards as faster devices become available.
Update: Corel Computer have recently announced the Netwinder Network Computer, which will use a 275MHz StrongARM SA-110. This is the first evidence of faster StrongARMs being available.
The card connects to the motherboard by means of a high-density edge connector. This connector provides better coupling between the circuit boards at the higher 64MHz bus speed.

The faster bus will improve the processor utilisation - the amount of time that it is doing productive work.
In the current RiscPC, approximately 20% of the StrongARM's time is wasted as it waits for data to be read from or written to memory. Whenever main memory has to be accessed, the processor has to synchronise its clock with that of the memory. With a 233MHz processor and a 16MHz memory, this imposes a heavy penalty; the situation will be less severe with Phoebe's 64MHz memory system.
Why not run the memory faster? The current SA-110 cannot drive the bus any faster than this! In addition, the complexity of designing the motherboard increases exponentially as the clock speed rises. PC manufacturers are having no end of difficulty with the new Intel 100MHz bus.

There are also plans for multiprocessor cards: potentially, four ARMs could be placed on the card.
Acorn will begin looking at multiprocessor cards following Phoebe's launch.
RISC OS 4 will not itself provide support for multiple processors, although Galileo will. In the meantime, Dave Walker intends to persuade the ARMLinux and RiscBSD teams to provide multiprocessor support through UNIX.

Floating Point Hardware is unlikely in the foreseeable future.
Acorn no longer have any influence over ARM's design decisions, as they represent only a small part of ARM's market.
Floating Point Units (FPU) are complex circuits, and take up large areas of silicon. Given that the majority of ARM's sales go to price, power and size sensitive markets, it is unlikely that full FPUs will be added to their processors.
Contrary to popular opinion, Java does not require an FPU. Reasonable floating point performance is desirable, but this does not have to be achieved through hardware. Currently, the SA-110 StrongARM is able to out-pace the FPU-equipped ARM7500FE at running Java.
With the improvements to the Floating Point Emulator (FPE) in RISC OS 4, Phoebe should match or even beat the floating point performance of the ARM7500FE.