Okay, so the final episode of Season 3 was so sucky that it completely ruined its otherwise awesome final arc, but to be fair to Russell T. Davies, he gave us two unambiguously great final arcs in Seasons 1 and 2 of NuWho, so there's still a good chance that the final arc of Season 4 could turn out very well, especially considering the recently confirmed casting news, regarding the number of returning companions, as well as the rumors of a certain Big Bad from the original series coming back.

Aside from the Black Guardian (who is STILL OUT THERE, just WAITING for the right moment to swoop in and fuck the Doctor's shit up), Davros is the last of the truly apocalyptic-level arch-enemies left unaddressed from the original series. A while back, Ian offered the following thoughts on the problems inherently posed by any portrayal of Davros:

From the discussion of spoilers for Doctor Who Season 4 on the KBOX forum:

I admit I'm not that enthusiastic because apart from in his initial appearance Davros has never been a favourite of mine. The first origin of the Daleks story was undoubtedly excellent, probably in the top three of my old series recommendations. Everything since then had been diminishing returns.

Davros seems to have been adopted subsequently by production teams who had run out of things to do with Daleks - "Davros can interact, use facial expressions, carry plotlines" - and every Davros appearance since then has seen the Daleks reduced to automaton killer robots instead of the wickedly smart mass-murdering racist conquerors they should be. In other words, Davros has usually been used because the writer and production team didn't have faith that they could do an interesting Dalek story.

Raynor's Manhattan story showed why she's a good script editor but a not-yet-ready-for-prime time Dr Who story - plenty of excellent little moments, plenty of high theme ideas, but a lack of ability to put them all together in a coherent effective whole. Dalek Sec played the Davros role in this one. The problem is that whatever monster a Dalek changes into it shouldn't - and probably in the terms of the series couldn't - be as scary of what it was before. Same is true of the Daleks and Davros.

So if they are bringing back Davros they're going to have to work damned hard to overcome the Davros factor and tell a story that maintains the prestige they managed to give the Daleks in the first three of their four new series outings. We'll see.

[...] By my reckoning there are two major old series elements still to exploit. Davros is one, and the Brigadier is the other. I still expect to see Nicholas Courtney turning up in Doctor Who, Torchwood, or Sarah Jane. We might yet see Yetis and their Great Intelligence as well.

[...] But mostly it feels like the "blast from the past" finale has had its day. I'd be up for the introduction of a major new monster that can rank beside some of the greats. I don't think we've had it yet, although there have been some worthy additions to the canon.

And the following was my response to Ian ...

Again, from the discussion of spoilers for Doctor Who Season 4 on the KBOX forum:

See, the thing is, I think the NuWho folks HAVE run out of things to do with the Daleks, simply because they've painted themselves into such a corner. They've already done the Lone Surviving Dalek story, the Legion of Daleks Who Somehow Hid From the Time War stories, and the Small Circle of Daleks Trying to Rebuild Their Numbers stories, so they're left themselves with no other stories to tell with Dalek Caan, that wouldn't somehow wind up coming across as a retread of one or more of the above stories, since that's exactly what the Daleks' most recent outing wound up becoming.

So, yes, in order to sell the return of the Daleks properly, I don't think there's any way around bringing back their creator, and moreover, the Daleks really need to be brought back for GOOD this time, because one of the biggest problems that's hurting the Daleks at this point, as characters that will always be brought back, is constantly explaining how they managed to survive the seeming genocide of their entire race THIS time.

Moreover, if Davies leaves after this coming season, I can't see him going without reintroducing all of his favorite Who villains first, and of the big-name big bads, Davros really is the last one left, unless Davies pulls a complete left turn and gives us the Black Guardian. Davies' writing style on Who is very reminiscent of Jeph Loeb's on Batman, in that I get a very strong sense that his inner fan is rushing to get through a Greatest Hits Parade of all the main players, just so he can put his own stamp on them.

[...] I really would like to see the Brigadier soon, if only because I'm afraid of Nicholas Courtney passing away before they get the chance. It makes me feel old to realize that even Ace is well into her 40s by now.

What I'd add to my above thoughts is what I'd forgotten, until this epic YouTube video inspired me to watch "Genesis of the Daleks" again online, which is that Davros is arguably the closest that science fiction has come to recreating the most terrifying aspects of the character of Hitler. Oh, sure, Darth Vader absolutely has him beat for a) pervasive use of stark Nazi imagery and b) just plain being a toweringly imposing motherfucker, but Vader's undeniable ability to intimidate, even before he utters a word (in the bad-ass voice of James Earl Jones, no less) is trumped to Hell and gone by how horrifying Davros' mentality is. Think about what sort of mindset someone would have to have, in order to create the most unstoppable and effective perpetrators of genocide in the entire universe, and then, watch the video:

Darth Vader is one of the most overrated fictional villains in history. He looks ridiculous, his backstory is lame, and he has exactly one good line in all six movies he's in.