It should be possible to write compliant boot loaders that load the OS image from a variety of sources, including floppy disk, hard disk, and across a network.
Disk-based boot loaders may use a variety of techniques to find the relevant OS image and boot module data on disk, such as by interpretation of specific file systems (e.g. the BSD/Mach boot loader), using precalculated blocklists (e.g. LILO), loading from a special boot partition (e.g. OS/2), or even loading from within another operating system (e.g. the VSTa boot code, which loads from DOS). Similarly, network-based boot loaders could use a variety of network hardware and protocols.
It is hoped that boot loaders will be created that support multiple loading mechanisms, increasing their portability, robustness, and user-friendliness.