Transferring USB port data to DE2-115 (GPIO or any other method)

Ambitious. Possible (I dare say) but ambitious.

Have a look at section 4.17 'using the usb interface' in the DE2-115 manual. Specifically the statement:

--- Quote Start ---

The most challenging part of a USB application is in the design of the software driver needed.

--- Quote End ---

So, you're hoping to recreate the driver required for the Picoscope and run it in the FPGA?

No, you shouldn't need any further GPIO. You will access everything through the ISP1362 USB controller. However, you'll have to understand whatever protocol the Picoscope uses, over USB, to carry the data. I doubt that is published...

Cheers,

Alex