If nothing in your current setup is holding you back, there's no point in upgrading anything. Upgrading and/or purchasing new stuff just to satisfy curiosity will get pretty expensive pretty fast. Below are three different scenarios I quickly came up with.
Upgrade only when you realize a specific need. For example portrait photography could benefit from a studio light setup and a couple of portrait lenses like 85mm f/1.2, 135mm f/2 or 200mm f/2 and perhaps a high resolution camera, like 5D Mk IV or 5D S (not the 5D SR for portraits).
If you are shooting sports or your own fast moving kids, then a fast telephoto lens or a fast frame rate sports camera might be in order. My personal favorites are 200mm f/2, 300mm f/2.8 and 400mm f/2.8, but some people prefer slow but more versatile zoom lenses like 200-400mm f/4. And the most sports oriented camera in the Canon lineup is the 1D X mk II, but a refurbished 1D Mk I would be very good too.
If you are into landscape photography, a sturdy but light carbon fibre tripod like Gitzo GT55xx, a tilt/shift lens like TS-E 17mm or TS-E 24mm or a high resolution camera body like 5D SR could be great choices.
Hold on to your money until you know what you need instead of what might be fun. Save your money until you are sure, and then don't settle for inferior stop-gaps, because you'll lose money in the end, but get the real deal instead.
In my opinion it is usually best to buy the item that you really need and want. For example if you need a fast 400mm f/2.8 telephoto lens, you might be tempted to first buy some plastic fantastic superduperzoom, then after badly disappointed you "upgrade" again and get some discount brand item, and then you realize it was a mistake too, and finally get the 400/2.8L. This step-by-step approach is the most expensive, and you have lost all the images you could have been shooting with the correct lens.