I had a post in another thread where Kittie was brought up and I basically said that I predict their next album will be more metal (if it is metal enough for this site will remain to be seen) than their last album. My prediction is merely a guess based on how they performed when I saw them live last Spring. They certainly played a lot of the death metal based songs, and while some songs had clean singing I didn't hear anything that struck me as 'mallcore' - conversely, I did see them several years before. I left that show early because I was bored, and they did lots of nu-metal stuff back then.
I think sometimes a shift in a band's sound can be heard before the album comes out based on what kinds of songs they play. Or conversely a band might show no signs of shifting their current sound.
In fact, this theory, if this thread lasts long enough, could be tested on two bands: In Flames and Killswitch Engage. I'm going to go see In Flames in just a couple weeks. I'm somewhat of a fanboy and I like even their new material. If they play mostly new stuff but avoid old stuff, that might indicate their next album is going to be largely similar to their last two albums, especially if they play stuff from their most recent two albums. However, if they play lots of stuff from Clayman and before, or at least more songs from that era than normal, they might try bringing back some of the old style of melodic death metal in their new album. I'll make my prediction based on their set list, though if anyone knows their set list from recent concerts they are welcome to share.
Killswitch Engage, however, might be in for a sort of "return to form" after recording their new album straight away after doing a whole tour in celebration of Alive or Just Breathing, which many consider to be the best Killswitch Engage album. A change in sound is inevitable, however, because Jesse Leach is doing the vocals. They did record a couple songs before the tour and one of those tracks leaked onto the internet. It was a rough mix, sounded alright but nothing too stellar. However, their first single from the album was released recently: http://www.youtube.com/watch?v=BsXi4C1KkrE
I think that song is awesome, definitely better than anything off their second self titled. Jesse nails it. He doesn't have that slight whinyness either, which I can't help but notice whenever I hear a Howard Jones era song.
Assuming Tony Iommi works on multi-year timescales, I guess recent performances can include not only his tour with Black Sabbath Lite (as in the version without Bill Ward), but also his work with Heaven and Hell and the album The Devil You Know. Riffing wise, it's probably a good bet that we're going to hear many heavy doom riffs like there are in The Devil You Know combined with the oldschool vibe of the Ozzy years on the new Black Sabbath album.
Local bands are more prone to showing their changing sounds on stage before on a recording. I've heard Gloominous Doom perform many versions of the same song - they would put the song out there, sometimes even in a primal instrumental state. The first time I heard them perform White Worms From Hell was as a raw instrumental, and I know recently they performed a new song that I don't even remember the title to also as an instrumental. Perhaps they'll play it tomorrow night.
I admit, my examples overall aren't the best examples. I'm curious though what other people's experiences were. Has anyone heard a band perform live and notice how they stuck to playing mostly old songs, then they go and put out an album that more or less is a return to form?