Unlike it was predicted last year, it would seem that AMD will keep the Duron processor line alive for a little longer, so reports x-bit according to some japanese sources:

Throughout the year AMD will gradually phase out Athlon XP "Thoroughbred" processors to leave more manufacturing capacity for the Athlon XP "Barton" CPUs. In order to fulfil the demand for lower-end processors, the company will introduce a new core called Thorton for low-cost microprocessors. CPUs based on the new core will have 256KB of L2 cache, just like Thoroughbred cores, and also will run at the same frequencies. Seems like Thorton is nothing more, but Barton chips with only half of L2 cache. I cannot state for sure, but I assume that Thorton is defective Barton with disabled 256KB of L2. Thorton processors will market under Duron brand-name later this year, starting from Summer, according to some unofficial sources.