Won't happen in a bios update, its an inherant absence in the 845e and 845g chipsets. Intel is going to release a new minor variation on these chipsets in the fall that officially support DDR 333. There are one or two chipset makers who use the Intel chipset who do support DDR333 *but* they are making modifications out of spec. Doesn't hurt things really but I doubt you'll see support in a simple Bios update.
That said, you can still hit DDR 33 rates no problem. If you are running a 533mhz chip(aka 133 fsb) just get good quality memory like Official Samsung ram over at newegg and run the ram in 3:4 mode. That gives you DDR 354. If you are running a Northwood 100mz FSB bus chip you should be able to OC it to 133FSB without any major problems then wash rinse and repeat as above.