I don't think Harley Quinn will make an appearance on this movie, mainly because it wouldn't make any sense without joker to mold her persona. There's a bigger chance that of The Riddler appearing, but i'm glad they're focusing on Bane (I still have my doubts with Anne Hathaway being Catwoman).
Also, I think it's too soon for a new Joker to appear. Not that there aren't any actors that can pull it off, but because there's something of special in that part. Nobody thought that Jack Nicholson's Joker performance could be matched, but Heath Ledger did it. Plus, I also believe that Ledger's death still lingers a lot on the cast's minds so, out of respect, they wouldn't include the Joker character again.
I'm eager to see how DKR plays out. TDK was my favourite Batman movie, after Batman Returns and Batman, so it has some pretty big shoes to fill.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"