Although I believe there may indeed be a new Intel Mac Pro coming, this seems like an awful idea to me. Why would you pour thousands of dollars into something that has already been EOLed?
1. It hasn't been EOLed. It is still for sale.
2. Thousands? Probably closer to several million for a limited update ( certification in several countries, marketing and sales overhead , contractor set up and management overhead , project management overhead , new firmware updates , board reflow, macOS base kernel andl library tweaks , compiler tweaks, etc. etc. )
Even if it something like $2M. Apple takes about 20% ( actually more but keep it conservative) so need a base of $10M. Say average Mac Pro sells at $6799 that amounts to about 1500 units sold to break even. If Apple thinks they could sell 5 or 6K what would not make sense is not to. If can sell 10K then leaving tots of money on the table.
$4M the break even around 3000 units.
The Mac Pro is no where near a 1M units/yr sell rate , but it is also likely not in the 4 digit range either. ( probably in the 5 digits). If it is in the 10's of thousands range even if they lost half the sales to M-series it probably still would make sense.
3. Apple hasn't EOL'ed the upper Mini... still x86. Haven't EOL'd the "edu" 21.5" iMac. ( can see it listed over in the 27" iMac buy page. And that unit is super old. )
If Apple comes out with a "half sized" M-seiries model then they could probably claim both.
1. "transition accomplished" ( M-series models in each Mac product category ).
2. Still selling Mac Pro with top end bandwidth and discrete GPU cards.
So far Apple has done a whole lot of nothing in supporting non Apple GPUs on macOS for M-series. If that is there plan for the next year , or two< then a refreshed Mac Pro would be both more than viable and likely still have a substantive amount of buyers even if the M-series Mac Pro siphons off most of the lower end of the market.
Apple raised the starting price of the MP about 100% from the old MP 2010-2013. Some of the folks they "left out" are probably the bulk of those who will buy a M-series MP that is priced closer to $3-3.5K.
4. This also could be saving Apple the money to build something to compete in the full size enclosure space. They can make more narrowly scoped M-series for the "Half sized" Mac Pro that lacks the I/O bandwidth to provision that many lanes. Take 4 MBP 16" dies and lash them together. Core count is high but coupled to an iGPU ( which probably means coupled to soldered RAM. ) . Single GPU and soldered RAM is pretty unlikely to win over most of the Mac Pro 2009-2013 holdouts.
5. The final problem that Apple has is that the > 16 core models of the current line up are grossly uncompetitively priced. They all have the Intel $3+ K "> 1TB RAM tax" slapped on them. It is going to be even worse once Zen 3 powered Threadrippers arrive by end of the year. Intel just introduced Sapphire Rapids (which makes the W-3200 look even long in tooth). The W-3300 do not have the excesss high capacity RAM tax attached to them. Refreshing the line up will allow to get to Mac Pro that is just kind of "bad" in $/performance ; not comically bad ( which pretty much is now).
A W-3300 refresh would allow Apple to "kick the can" on trying to address the top end of the workstation market another 3-4 years from now ( so another year or two until have to kick in chip design resources ). That is probably fine with them because the primary focus is getting the Laptops and iMacs on solid ground. They can measure the "half size Mini " and "big chip" iMac updates and see how much is left of the old school Mac Pro crowd.