No, that wouldn't work, because the Miditech USB MIDI Host has MIDI Out but no MIDI In. To connect two keyboards together when both have USB-MIDI, you'd need to use two USB MIDI host devices-- connect each one to a keyboard via its USB connection, then connect the MIDI Out port of one host to the MIDI In port of the other host (and vice versa if you want to have two-way communication between the two keyboards). For instance, to control a PSR-E453 with a DGX-650:
DGX-650 | USB To Host port --> USB MIDI Host #1 | MIDI Out port --> MIDI In port | USB MIDI Host #2 --> USB To Host | PSR-E453
Unfortunately, these USB MIDI Hosts can be a bit pricey if you need to buy two of them. Another option might be to get a USB Host MIDI Router from Sevilla Soft. As long as both USB-MIDI keyboards are MIDI class-compliant, you should be able to connect them to a powered USB hub, then connect the USB hub to the USB Host MIDI Router, and configure the USB Host MIDI Router to route the MIDI from one keyboard to the other.
However, if you already have an iPad or laptop or computer, it would probably be cheaper to just connect both keyboards to the iPad or laptop or computer and use software to send the MIDI from the DGX-650 to the PSR-E453. If both keyboards are MIDI class-compliant, you can connect them to a powered USB hub, then connect the USB hub to an iPad using a Camera Connection Kit-- or you could buy a USB-MIDI Bluetooth adapter from Yamaha for connecting one keyboard to the iPad via Bluetooth, and connect the other keyboard to the iPad using a Camera Connection Kit.