Digital Signal Processors (DSPs) are microprocessors that have the potential to minimize your investments in a full set of surround sound speakers.
Yamaha has been developing the YSP-1 and YSP-800 systems, which are useful if your home theater isn't quite ready for a multiple-speaker setup. The YSPs are essentially one-box receivers, which can come in handy if you can't afford or don't have the space for the typical 7.1 surround sound design.
As of now, DSP technology has yet to come into its own. Home theater buyers are still accustomed to their multi-tiered setups, and the YSP systems still can't match the surround systems today, but that's no reason to expect that it won't in time.
Until then, home theaters with 5+ speakers are still the norm. And it's always possible that manufacturers will greatly prefer the proliferation of products to buy (as opposed to one all-encompassing receiver), but you never know - if your living space or finances aren't ready to commit to the larger setups around: this may be the time to hold out.