Apple Silicon is a totally different thing from the past models and it's really capable from what I understand.
Yes, and it will almost certainly run rings around your 2008 model CPU wise - just don't get sucked in by the "8GB on M1 = 16GB on Intel because unified memory" myth - if the 'memory pressure' reading on your 24GB 2008 is going into the yellow/orange during your regular workflow then you could probably do with more than the 16GB maximum of the current M1 machines.
Also think about what sort of display you want - the 24" on the M1 iMac is probably all-round better than what you have at the moment, but larger displays are available these days, so you may be better off with a M1 Mini plus the display of your choice. Or, if you want all-in-one, the anticipated 5k iMac replacement should have something
at least as good as the 27" 5k display (which is a thing of beauty) and possibly a larger/higher res upgrade. Also, none of the M1 macs can support more than two displays (so, only 1 additional display on iMac) which is something expected to change with the new machines. Also, the M1 GPU might completely thrash Intel integrated graphics - but that is a low bar, and the M1 is only really comparable to a so-so, several years old desktop GPU (which is still something, for a 15W SoC, but that doesn't count for much on a desktop).
It's always the case that, if you wait, something new will come along, but in this case we've really only seen half the story with Apple Silicon. The M1 is a chip optimised for tablets and ultraportables - not a graphics professional's main machine - and while the advance is such that it gives the last Intel "Pro" macs a run for their money, I think that's only a transition phase until the "Apple Silicon Pro" (ie. M1X or whatever it gets called) machines come out.
They need to be a substantial, clear blue water,
upgrade c.f. the current higher-end Intel Macs - the M1 isn't that.
In this case, your previous machine is still going strong after 12 years. You're probably not going to repeat that feat, but if you want something that is going to stand the test of time you might want to set your sights a bit higher than "better than my 13 year old Mac" - I'd at least wait for the M1X machines to show, if not give it another year for the early worms to get the bird (speaking as someone who bought a 200
6 Mac Pro that ended up on premature door-stop duty).