You don't have to move to an HDMI AVR. There are some things that become better if you do.
1. Room correction. The more modern room correction functions (Audyssey, et.al) are effective at compensating for room maladies, making your sound better.
2. Component source up conversion. If the video chip is advanced enough, some AVRs are capable at taking an input signal and upconverting well.
3. Lower number of cables. Makes life simpler.
4. Newer technology. Moderns AVRs can decode lossless sound (TrueHD, DTS-HD-MA) when fed a bitstreamed source. 3D may not matter now, may later.
5. Some AVRs provide firmware upgrades via network.
6. Streaming music to the AVR. Some can get music from the network, with a server based on a PC or network hard drive. You can use MP3's or lossless formats like FLAC on SOME AVRs.
7. Different speaker options. Some new AVRs have the ability to add 'wide' or 'height' speakers, adding sound to the frontal three speakers.
8. Control of the AVR from an iPod / iPhone and streaming music from them through a bluetooth device.
Again, you have to judge if the newer features are worth the upgrade. The room correction feature for me was key, as well as the lossless formats.
You can get the lossless formats on your current AVR, though by running 5.1 analog cables from your Bluray player to your current AVR, but only if your bluray player provides 5.1 analog out connections, and if the Bluray player decodes TrueHD and DTS-HD-MA internally.
This can only be done on the analog lines, since digital connections outside of HDMI can't carry the signals. Your AVR doesn't decode those signals anyways, so you're stuck with analog.