Networking is already built in. So are Audio and Video (in fact AS has specific hardware video accelerators - basically every M series except for the original M1 has built in Afterburner). Raid cards are interesting but again the storage you can get on card is already pretty huge.
What about the next type of card that doesn’t yet exist?
Without a high speed bus to the cpu, it can’t be invented.
And thunderbolt is great but it isn’t anywhere close to the full pcie5 x16 spec.
Also. Built in 10 gig is ok but the processing power in a new pro will be enough that we may want 100 gig networking or faster to access massive data sets on enterprise SAN storage - to get data in and out of it fast enough for the compute hardware to not be sitting idle waiting. Just as one trivial example.
10 gig networking isn’t fast in 2023 and even 1-2 consumer SSDs will outrun it by an order of magnitude.
Give it two years and single consumer SSDs will keep up with 100 gig Ethernet.
We need slots at this end of the market.
If the new pro is going to be aimed at AR/VR content creation I can easily see the bandwidth requirement. I know carmack reckons something like 16k per eye at high frame rate is required as the end game for actually good VR and we aren’t there yet.
The bandwidth needs are huge.