When you say recently do you include an entire decade? O_oI don´t agree. Law of diminishing returns here. Dual cores are used for 15 years now and still on a lot of systems. Plenty for basic tasks. We recently made the jump to quad cores as the basic mainstream option (most mainstream laptops) and I think it will be a long time before we need 6 core as a bare minimum. Even upcoming Intel laptop offers (10nm) are 4c/8t chips, because that´s plenty, not 6 cores.But how long is Intel going to be able to sell the defective core chips as low-end chips? I don't think they have very long since with the way things are going (soon) six-core processors are going to be the bare minimum. In other words, a Core i3 is going to be a six-core processor.
Core counts will only go up to certain value. On HEDT for really serious productivity work/servers, yes, the more the better, but it was always the case, 16 core CPUs are not new. For mainstream I doubt we will need more than 8 cores, max 12, for at least a decade. We will not see 32 core CPUs coming to mainstream as bare minimum anytime soon, and the future CPU releases (2021, 2022, 2023) will not focus on having more and more cores. It will be about IPC improvements, DDR 5, Pcie gen4, lower power consumption.
If you try to use a "simple" i5 8400 you will see that it struggles to reach 25%/30% usage on anything that isn´t game related or intensive productivity task. Even with 5 twitch streams open at 1080p 60fps, 5 youtube tabs, instagram, facebook, microsoft word, etc. Is just overkill. We use it because we are enthusiasts or gamers or content creators. Quad Core and 6 core CPUs will stay for a long long time. The next big evolutions will be litology + power consumption wich will make everything smaller. Thinner laptops with still great performance. Smaller laptops that can fit on your pocket and you can open them to a regular size. Mini Itx PCs more and more popular with small GPUs, small motherboards. Tbh in 10 years I suspect most PC users will have a PC on the go that they connect to their monitor or Home TV at home, and bring it with them outside where they want.
6 cores are fast becoming the norm and that's a good thing. Games already work better on 6 cores and most software can take advantage of the extra cores. For too long Intel has given mainstream users the finger with just 4 cores, thank god Ryzen was a success.
As for intel's new 10nm 4 core chips.... the only reason they made them 4 cores is because 10nm is broken and they can't make high performance or high core count CPUs. Their yields on that process node are at rock bottom. They are literally forced to continue using 14nm+++++ till late 2020 unless they magically resolve all problems.