What some of these other guys said. The most storage you can get in a tablet is the new 128GB iPad. Or you can get a Samsung Galaxy Note 10.1 with 32GB built in and add a 64GB microSD, for 96GB total.
But, what's the point in either of those? You may as well just buy some microSD cards and use them in your GoPro (or whatever) and take them out and keep them (versus transferring the files to a tablet). If you transfer them to a tablet that has no microSD slot, you'll run out of space quickly. If you are using the tablet to transfer files from your GoPro microSD to the tablet's microSD, you're not really doing anything but wasting time - 'cause in the end, you still just have the files on a microSD card.
OTOH, if you get a Note 10.1 (and there are others, too, I just know what I have) and an external USB drive (and the right Samsung adapter), you can take the microSD out of your GoPro, put it in your tablet, and then use the tablet to move the files from the microSD to your (large) external USB drive.
But, since your original purpose was to eliminate use of an actual hard drive, that doesn't really seem to fix anything for you.
Iron Butt # 4999, (former) WERA/CCS EX # 666, AMA Life Member, Drummer, Bassist