Green Giant still makes Mexicorn, but I believe they have dropped the name Niblets from it. I bought Mexicorn as recently as ten years ago (my mom used to serve it with a chili relleno casserole she occasionally made.) The peppers in Mexicorn are sweet, not hot, so it's not a very exciting product.
I've always thought of succotash as corn and lima beans together, but maybe corn and "anything" else counts as a "succotash"?
Thanks to you both for letting me know it's still around after 66 years! So obviously, there are people out there who like it.