Figuring out when to upgrade your home theater equipment is a tricky prospect. On one hand, new gear offers updated technology, more features, and the lure of the latest and greatest. On the other hand, how much better is it compared to what you've got?
Even if you haven't been bitten by the upgrade bug, there's always the looming spectre of obsolescence and future incompatibilities.
There are a few guidelines you can follow to figure out if it's worth upgrading now or better to wait. Plus, there are a few trends you should be aware of in regards to your current gear and upcoming tech sunsets that could make it obsolete.
When it comes to TVs, and all video products for that matter, the most important feature is HDMI. The High-Definition Multimedia Interface is the standard connection between displays and all modern HD sources.
If you've bought a TV in the past few years, it's got HDMI. If your TV is older, and doesn't have HDMI, that will be a problem going forward. Many new sources, like the Apple TV and Blu-ray players, output HD via HDMI (in the Apple TV's case, that's its only video output). If you have an older HDTV, and want to get a Blu-ray player, know that it can only output standard definition via its legacy analog outputs. With the best picture quality of any source, Blu-ray players are definitely worth getting.
3D is the biggest new feature in TVs, just like at the movies. If you're interested in 3D, you'll need a 3D-capable display (most new models are equipped for 3D), and a 3D-capable Blu-ray player (also standard in most new models). These components will be connected via HDMI. At the moment, all 3DTV setups require glasses.
If your theater features a projector, these have improved dramatically in the past few years. 3D has required manufacturers to push the light output of projectors, so most new models are brighter than their predecessors. This means you can upgrade to a larger screen if you want. Keep in mind, though, watching 3D means using similar glasses as those used with 3D TVs, so you'll lose some brightness (in which case, maybe your current screen size is fine).
On the A/V receiver side, the biggest improvements are HDMI switching and room EQ. With multiple HDMI sources, being able to switch them with a single button-press makes life a little easier. Room EQ, built into many new receivers, takes measurements of the acoustics in your room, and creates a custom equalization that improves the overall sound, without changing your speakers. The better systems, requiring trained custom home theater installers, offer more advanced room EQ for even better, more accurate, sound.
Though speakers haven't changed much in recent years, advancements have been made in the sound quality of in-wall, on-wall, and thin speakers. What were once merely nice to look at can now offer freestanding-speaker-rivaling sound quality.
Your best bet is to contact a local custom installer. They'll be well-versed in the latest technology and will be able to appraise your current setup for potential upgradability issues. Chances are, they know the home theater equipment you have and how much better the latest versions are.