I was in a similar situation. I needed to replace an aging iMac and MacBook Pro combo. I love the iMac, and thought I would be upgrading to a 27" M1 iMac that would surely be coming shortly after the 24" M1 iMac was announced. Obviously, that never happened.
I ended up ordering the Mac Studio the morning it was announced. I love the fact that I could get more RAM and storage than either the iMac or the MBPro and more ports for different connections than the iMac's limited 4 USB-C ports. The problem became what display to get. I thought, like so many others, that I would have to spend the money on Apple's ridiculously overpriced Studio Display. Thankfully I didn't have to.
What I ended up getting was a 34" 5k/2k screen. This gave me the ability to actually use the full 5120 pixel width resolution without the GUI being too small to read like it is on the 27" iMac. The color fidelity and sharpness is just short of retina quality (NOTHING beats Apple's display quality), but it's close enough that I have no problem with it at all (and I'm a graphic designer, so a quality display matters to me).
For $1,199, I got a larger screen with the highest resolution possible, a stand that allows for height, tilt and pivot adjustment (extra cost for the Apple display), HDMI, Display Port and Thunderbolt connection ports for connecting to the Mac, and extra USB-A ports for older peripherals. As a bonus, I don't have to deal with having a completely separate OS to update just to view the screen! The Apple screen literally has no benefit to me.
As far as speakers, a cheap pair of $20 speakers from BestBuy gives me better sound than Apple's built-in speakers on the Studio Display.
The plastic vs. aluminum body is of no consequence to me. It's a 34" display, I'm not throwing it in a bag and carrying it around. While the unibody design of the Apple displays are nice, they mean nothing to me in day-to-day use. I'm not so vain that I have to have the display match the computer color.
I don't expect Apple will be shipping another iMac Pro. That Mac was made to temporarily replace the cancelled trashcan Mac Pro. I do think Apple will eventually make a larger iMac, but it won't be as flexible or as powerful as the Mac Studio (if they're running the same processor). So it really comes down to what you're going to use the Mac for as to whether it's worth waiting for an iMac.