My opinion about technology chasing:
1) USB 3.0 took about 5 years to populate the market with decently reliable products, with some products totally cannot make it.
even today there are products that comes with 2 USB 3.0 and 2 USB 2.0 and i don't even understand why can't it all be USB 3.0. that made me had to remember which part is the faster one.
2) This USB 3.1 is only 5.0gbps speed implementation. Throughput of USB 3.1 is 10gbps. So now even buying current MacBook is going to be obsolete.
3) Unless you need 5K screen to work (you can use an iMac 5K or some manual arrangement on current machines), Thunderbolt 2 is a good 20gbps of bandwidth, enough for 4K screens. The MacBook Pro Retina have enough USB 3.0 ports plus TB2 ports.
4) TB3 products will need at least 1-2 years to come back to easily support 5K screen. TB3 machines will come only end of 2015 or 2016.
5) Only SSD can truely utilise USB3.1 bandwidth of 10gbps or about 800~900MBps. But my question is, do u need it? TB2 offers you 20gbps or about 1375MBps in real world and there are products readily available. TB product implementation is generally more reliable than some USB 3.0 products. Again, unless you are doing commercial stuff, I don't see why you need poor implementations of USB3.1 stuff for the next 2 years.
6) The 12" MacBook is clearly for those who only do some paper work, type their report, emailing, web surfing and other light stuff. The end users are lightly to have Free Wifi and using cloud services or storage would be feasible backups. Such users are unlikely to backup their system and would not bother if their system fails, simply because they have the backups online.
yes, and many of the current mba users just use it for web surfing and this machine is more than capable to do just that.
7) users would include university students, corporates running on cloud services as well as your run of the mill general users who dont do Photos or Video stuff.
8) There are the 13 and 15 rMBP which offers the solution yet people are in disbelief about why Apple make such a product. It is like a person who do not eat fish asking why is the fishmonger selling fish when I don't eat.
apple won't be that stupid to make a product that nobody want. even if nobody want, they will somewhat still manage to make you want it.