Serial port - you can get a USB serial port adapter - serial device lives on.
floppy drive - again you can get USB floppy drives - your floppy data is not lost.
Ditto on PS/2 port.
All of these are slower than USB, so USB port works well.
FW400 is effectively faster than USB 2.0
There are no adpaters to my knowledge that allow you to go from a FW camcorder (and other devices) into a PC (Mac or Win).
See, here's the thing. You still have a FW option. It may be $200 more, but if you really
need FW, you can have it. In the case of the floppy drive, serial to USB, and PS/2 to USB, all of that required you to buy the external device/adaptor/upgrade your old mouse to the new mouse. For a couple hundred bucks, you can buy a new camcorder that probably matches or exceeds the specs of your old one, or you can stick with your old one and buy the more expensive laptop.
There is always an option and always a sub-market who's needs wont be met by a particular product. The MacBook caters to the most likely group of people to buy a $999 laptop. People who need a computer for taking notes in class, sending email, watching youtube videos, managing pictures of their kid, own a Flip Mino/HD or other mass storage video device, and who want to use iTunes to listen to music. Under most circumstances the average student, house-spouse, non-creative professional, or businessman does not need firewire.
Anyone who has a FW camcorder or HDD needs to ask themselves about the cost of upgrading their camcorder vs choosing to spend $200 more on the pro.
I own three Camcorders in the professional range of products. All of them use firewire. These are multi-thousand dollar cameras. It would be a significantly greater cost for me to replace them then to choose to buy the higher end MBP (not that I'd consider the entry level MBP in the first place). I also have a couple dozen FW drives, although they all use USB or eSATA as well. Do I value the speed of FW enough that I would upgrade to a FW ported computer? Yes. It is not an argument about what is a better standard, it is an argument about what makes most sense in a consumer level product.
We all make value choices. Apple made theirs, now the consumers can make their own.