MIDI ports didn't really go to USB ports. the MIDI standard has not changed (in 30 years!). the manufacturers of keyboards are simply including the MIDI/USB adapters like slart has linked to INSIDE the keyboards.
I would be seriously surprised if you'll find a "professional" keyboard without traditional MIDI I/O ports in addition to the USB port. Why? because professional live players tend to use more than one keyboard and that requires MIDI Merge or at least MIDI Thru for the use of MIDI channels to control different keyboards.
the "consumer" type keyboards have done away with MIDI I/O ports and left only a USB port because the consumer type user doesn't typically need to control more than one channel and they typically just connect the keyboard up to a computer which would require the adapter if the manufacturer didn't include the adapter in the keyboard.