I think Apple sees Thunderbolt as the gateway to making even thinner products. Anything that you only sometimes need can be excluded but added externally via Thunderbolt.
Exactly, and I for one welcome the change. And yes, for the record, I often find the need to use Ethernet cables. I'll happily use an adapter for those occasions though.
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Not really sure how this would be a problem for the pro.. still poor graphics, little memory/no expandability and a much less powerful ULV CPU... this isn't for professionals.
Removing the Optical drive allows for quite significant redesigns that would allow for thinner and lighter laptops. They could easily maintain user replaceable ram and the high-end CPUs and dedicated GPUs. Now, if in the end they must maintain a certain minimal size that allows for ethernet ports, sure throw one in. But if they can get it to the size of the MBAs while keeping the dGPUs and quad core CPUs, I say chuck out the bulky ports.