Not me. And even if they did a duet, it would still be all about Gaga because she's 1000x better than KP. Gaga's voice is superior. No. It shouldn't happen, Gaga cannot lower to trash.
I Amore Gaga, and I like Katy - but no, I don't think it's a good idea. Their styles just don't match; they won't even look good together. Besides Gaga has più powerful voice, and Katy will probably sound kinda bleak - which obviously won't do any good to the song.