There are many people who will get on the 'upgrade' bandwagon, but in reality, there is very little reason to do so unless circumstances force you into it. Amplifiers have a sound that some like, others don't, and those with golden ears complain about ad nauseam.
The obvious greatest downfall of the older system is that you can't take advantage of the newest HD codecs and can't handle the newest UHD resolutions.
Now, with a limited system setup that you are using, this is your call. If you don't miss the upgraded sound of HD audio, and your Blu-ray Disc player is not a UHD version, then call it a day and enjoy what you have. There are also UHD BD players which have dual HDMI connections so you can route audio and video separately from each other, just in case you do have an older AVR.
I'm all about getting the most mileage for your money if you can, and if it ever breaks down, or you really want to try out HD audio and the joy (and headache) of 4K video, then there is a pretty penny or two you can drop on new gear that supports all of it. But, doing so, when you really are happy where you are at, seems like it is a waste. As well, you know you really are happy, so it doesn't make a ton of sense to spend good money at this point.
A personal aside, which is a point that bugs me, is that it drives me nuts that the major manufacturers don't make lower priced, full featured AVRs which don't include amplification. In my setup all I need it a few HDMI inputs and processing and I could run it to separate amplifiers. This would allow people to upgrade their AVRs more often without the incredible expense that seems to go along with non-amplified AVRs, or those which include 7.1 pre-outs.
Enjoy what you have. Upgrade only if you want to. Don't let the industry lead you along.