It is quite probable that two of the factions that can be joined will be the pro-Empire and the anti-Empire sides, I would think. I hope that there will be a way to join the church in Skyrim, Imperial Cult or something like it.
But I do think that the Mage's Guild will be a lot different this time around, as will the Fighter's Guild, maybe something closer to an Adventurer's Guild instead.

I hope that there are no Mages Guild or Fighter's Guild at all in Skyrim, only various factions with cool names, compelling characters with interesting backstories and quests on the level of "Whodunit?"

It would be great if there are factions in conflict with each other that require the PC to make difficult choices. For example, it could be that if you choose to side with one faction or another, you lose the opportunity to get unique artifacts or spells, etc.

And I really hope we don't have to hear every NPC tell each other that "the Fighter's guild is hiring."

I'd like to see the Imperial Legion. A legion struggeling to keep its grip on the empire makes for a good story.

I hope factions will be A LOT deeper than "simply" opposing faction interests. Like in FONV where you do all these complicated and intriguing quest lines just to help you make up your mind on who to support, and choosing and dedicating yourself to one side is kinda gradual, and when the decision has to be made there is NONE that really fits your bill, and where your early impressions flips around when you actually meet the people you thought you were going to hate Unfortunately I think this requires a very strong characterization of the various NPCs, and Todd has already said they will be a lot weaker and generalized compared to FONV.

I thought he was referring only to companions and companion quests.

Or did you get this information from a source other than the podcast interview? IIRC, in the interview, his only comment about factions was that there would be a lot of them and he would talk more about them in the future.

I hope that modders will improve the NPCs a lot...I want them to be like Cliffworms' added verbal lines.

All I know is that I want Dark Brotherhood assassination quests to not have an end, to just always be able to go assassinate someone...

This is the bit from the pocast: "We are approaching it in a different way. I would not expect the deep personalities and uniqueness with a low number of companions. We are aiming for a much, much higher number of companions that you can hire or they become your friends and they come with you. The general direction is to make it a bit more dynamic, and have more people that you can decide to have come with you. And in that we sacrifice them having a lot of depth or personality or individual stories. And there still will be some like that."
To me the last but implies that there are still a few characters with more of a story behind them.

I think the factions will be made MORE AWESOME!!!

I took it to mean that the NPCs who can become companions will have less "depth of personality/individual stories" compared to the companions in a game like FO3 or New Vegas, simply because there will be more possible companions. However, there will still be a few NPC companions with deeper backstory/personalities.

I don't think this statement provides any information at all about the comparable level of backstory or character depth for non-companion NPCs or factions/faction-related quests.

why would anyone think that factions wouldn't return? That was one of the worst questions asked in the podcast to be honest and should have asked a better question.

I'd like it if you could somehow create your own faction.

Yes that was what i thought