Peter Capaldi started off great but he was ultimately wasted. It's like the writers never could get a handle on what this iteration of the Doctor was supposed to be. I liked that he started off a bit grim and sardonic, but then he ends wearing 3D glasses and playing guitar. It became stupid. I haven't started the recent series as yet, as I usually catch up just before the Christmas special.
As for the new Doctor, last I heard the odds were in favour of Luke Treadaway, who is the twin brother of Harry. I smiled when I read that, because when I first saw Harry Treadaway in Penny Dreadful, I though he would make for a great Doctor should they ever go back to casting younger. (in case you already didn't know, HT is playing Brady Hartsfield in the Mr Mercedes TV series). That said, British bookies are historically way off-the-mark when it comes to predicting successive actors for this role, so I'm sure it will come as a complete surprise to the fans. Tennant and Smith were lightning-in-a-bottle casting, especially as they appeared back-to-back. It'll be difficult to replace that, and I hope they don't try. Just get a grip on the character, and remember why the fans love him: he's an alien outsider with a fondness for Earth, a scientist, an explorer, a being who controls time and is totally unpredictable.
The one thing I want to see more of is other rooms inside the Tardis. I really liked the 8th Doctor's (McGann) adventure for this. And no, I don't think the Doctor should be female.