This are all speculations, feeded by rumors and the latest PC laptops.

case

Apple always said the 12" Macbook is the "future of the notebook". So it's clear that the new Pro`s will look like bigger brothers of the 12". The thing I like the most of the 12" is the color! Space grey on a Macbook looks awesome! It's darker than the normal aluminum unibody. They should just add more than one USB-C port...

So I hope the new pro will be also available in space grey and perhaps in pink, sorry rose gold :-). My guess is that it will be 15%-20% lighter and thinner. So around 1.5 cm height and 1.7kg weight for the 15.4". The HP Spectre is even more extreme. It has some cool things, but to much bling for my taste.

display

If the 12" is the replacement for an Macbok Air and Macbook, than perhaps Apple could create an 14" and 16/17" Macbook Pro. I think the air 11" will be phased out, the bezel are just to big on this model. If the bezels are getting smaller they could potentially use bigger displays (looking at you DELL XPS). In forums a lot of people are missing the 17". It will be interesting if apple can/will put a UHD screen into these machines.

Current 15.4" Retina Macbook Pro display specs: 2880x1800, 221 dpi used resolution 1440x900 Possible UHD Macbook Pro: 3840x2400, 283 dpi (16"), 266 dpi (17") 1920x1200

Take a look at the DELL XPS 15 (2kg weight). Awesome 15.6" 3840x21860 display.

CPU & RAM

My bet is they will be using a mobile i7 quad core part as usual and a pricy build to order option to use a mobile Xeon part with ECC ram. Read on to know why this is important for me (look also here Advantages of ECC Memory. I use ZFS on Linux servers which is really awesome (snapshots, pool manger, intelligent compression, etc.) and also already on my Macbook for virtual machine storage. ZFS is the only file system I know which is good supported on different UNIX operation systems like OS X and Linux. Its recommended to use ECC ram for ZFS. This would make the Macbook Pro a really pro machine like the Mac Pro.

This is the thing I want the most from the next Macbook Pro. Then I could say goodbye to creepy time machine backups and make reliable backups to linux servers in seconds!!!! Please please.... Crossing fingers.

I also hope that apple adds native ZFS support to OS X (macOS?) like it was rumored some years ago. Ubuntu 16.04 did it!

On the PC side there is for example the Thinkpad p50 with Xeon CPUs and up to 64GB ram. I guess Apple won't go that far, but 32GB could be an option. The Xeon E3-1535M also has quite a beefy integrated GPU, smells like a Apple request for the model without separate GPU.

GPU

When the first news of AMD Polaris 11 GPU and earlier HBM memory (AMD Fury) came up, I saw a potential dream laptop GPU. 14nm and HBM memory reduce the space and the power the GPU needs. This could be really a huge step forward for laptop graphics. It looks almost like Apple demanded this.

The new Polaris parts also have hdmi 2.0, so you can connect a gorgeous UHD screen. Polaris supports h.265 encode and decode, perhaps Apple can finally start to use h.265 also for iOS devices. At the moment Apple has the problem that they could easily add this to iOS devices with fixed function hardware, but not to the desktop. This could also enable UHD Netflix streams on the Mac. A powerful graphics card is also needed because of thunderbold 3. Finally an external iMac 5k alike screen is possible with the bandwidth which thunderbold 3 provides.

They could it also make it the other way around and put a fast GPU directly into the external display and connect the GPU via thunderbolt to the Macbook Pro. Like a razor core directly built into the display, this would make the laptop smaller / lighter. Or you could use it as an extra GPU for more processing power.

SSD & Networking

Already the current PCIe NVM integrated SSDs are blazing fast with 2GB/s. They can only get faster... It's a shame you can't connect to a network with not more than 1 Gbit. With thunberbold you can connect to fast direct attached storage, but the default wired networking speed is very limited with 1G ethernet.

There are third party 10G ethernet adapters which are bulky and pricey. The wireless standard 802.11ax (5GHz, around 10G) will replace 802.11ac as default standard at some time, but this still take some years.

Another standard is 802.11ad (WiGig) which operates in the 60GHz Band. This wireless standard has around 7G bandwidth, which would be a welcome upgrade. The drawback of 60GHz is that it can't pass walls. For example the Acer TravelMate P648 has 802.11ad.

Or apple has a suprise for us with Li-Fi for faster wireless connections with light.

Waiting for WWDC :-)

Can't wait for the new Macbook Pros. This could be a big leap for Macbook Pros. What I like about apple is that they wait until all needed technologies are available to build a balanced product. Every part is as fast as needed to work together without creating a bottleneck.