There are some minor hardware differences depending on when you bought your deck and random chance. If you buy a brand new deck for example you may find you have a different heat shield than in most of the older tutorial videos for the deck.
Another example of differences is that two different styles of thumbstick were used, and until recently you were limited in what replacement thumbstick upgrades would work depending on which type you had (now they have universal upgrades that work with both kinds).
I’m wanting to buy a steam deck, but I wonder how close they are to releasing an updated version. Is there any indication that they will be doing regular hardware updates on it?
They've been making steady revisions and improvements to the hardware since it was released. Better buttons, better acoustics on the fan, new heat shield, etc.
There's no way to know when the next hardware revision will be, but if you buy it now you'll be getting a pretty great piece of hardware that has had all the major kinks worked out.