Bit Tech reports all new hard drives will feature the "4k advanced format". Western Digital was the first to announce a hard disk with this technology, but it appears that the whole industry is behind the transition.
To quote Seagate PR directly: "International Disk Drive Materials and Equipment Association (IDEMA) have agreed that beginning January 1, 2011 all new product releases with SATA interfaces will support Advanced Formatted media."
The 4KB sector size is an advancement from the 512Byte sector size that all hard drives (as in, mechanical media) have adhered to for the longest time. The larger sector bring efficiency advantages because as the total size of drives increase, less sectors have to be used, and less ECC data overall has to be written, physical saving space. The downside is that there are issues of compatibility with older operating systems, however the drives will contain a "512B emulation mode" (at a performance loss) for the foreseeable future.