SSD replaces HDD: Apple has done this on the Macbook Air it introduced last month and it hasn't encountered much trouble. What SSDs bring to the computer can be seen at the end of the video below. The only barrier of SSD is the high price. But if the number of orders is large, it is likely that Apple will have a good price and we will pay some part of the price.
No optical drive: The optical drive has become a standard in notebooks. However, with the development of flash storage formats, the ability of optical drive to follow the path of the floppy drive is entirely possible. There are quite a lot of laptops that have optical drive. Apple can do the same thing.