1) Microsoft Games Studios - Based on many preditions, the 360 is set to sell more than the original Xbox, and if MGS publishes a consistent stream of games (and not refusing to publish certain niche titles this time! *cough*Phantom Dust*cough*Oddworld*cough*) they'll do great.
2) Bungie - One hit wonder, nowadays. I'd love to see them do something more interesting than another Halo game, but it'll still do really well. Maybe not as well as the second one, but...
3) Konami - Did very well sales-wise this generation, although a lot of that was whoring anime licenses and Bemani games. Drop in quality IMO this generation - Suikoden 4, Nanobreaker, and LOI seem to attest to that... although the MGS games still kick ass. Hopefully will make better games next generation.
4) Square - Poised to have a banner year this year and next. Not only in sales (KH2, FFXII) but in the quality - Radiata Stories, Grandia III, DQ8. When they get some more portable games out, that'll help out a LOT. Diversifying platforms, ESPECIALLY to Nintendo, will surely help (CC seemed to do rather well on Cube and DoS and KH did well on GBA).
5) Capcom - Shame to see them doing so poorly. I'm really impressed how they've turned around from the "marginal updates year after year" laughing stock of the industry to one who has released some of the most innovative stuff this year. RE4, Okami, BOFV

Q. But they really lost mainstream mindshare. Don't like what they've done to their 2D fighters. Could be in some big trouble if they don't release more grade A titles/don't support the "right" system next gen.
6) Namco - It's really difficult to say. I like how they're taking a risk in bringing more esoteric titles to the states, but they haven't really been advertising as much as usual. Will probably gain their income from the same hardcore gamers they've always gotten it from.
7) Electronic Arts - They'll do fine, but probably sell a less than these past few years till the next generation "settles in".
8) THQ - I can't believe this company's been around for this long. SOMEONE has to be buying their games... but who?
9) Bioware - I can't make a conclusion since I don't know how they've fared in the past. Is Jade Empire doing well? Did KOTOR do well? They'll probably always have the hardcore PC gamer market, but then again I don't know how big that is.
10) Nintendo - They'll always have the portables, IMO. Nintendogs will probably be a bona-fide hit in the states, moving more DSes. I can see a DS price drop for the holidays, which will help them, and Zelda will be a nice boost to them. Revolution is such a wild card it's not even funny. Could either make them the laughing stock of the industry, or make them the laughing stock of the industry with the best selling platform (like with the DS). Who knows?
11) Rockstar Games - Another one-trick pony company. I don't remember any of their non GTA titles ever making it big, critically and commercially. Next-gen GTA is sure to be huge, but some people are saying that that series time has come (I don't think so, though).
12) Take-Two - Should do nicely now that they have the ESPN games under their belt. But I'm sure that losing the Madden license provided a crushing blow to them.
13) Atari - Not sure how much longer they have. They just haven't been getting the mainstream hits and usually pick some pretty poor games to publish.
14) Majesco - I don't know too much about them, but BloodRayne has been a minor hit for them, apparently. If they publish more niche stuff like Phantom Dust, and less licensed shovelware, I can see them building up a reputation for that.
15) Midway - Some of their games have done well critically, but I can't think of any hits Midway has had. The MK series still does okay, though it's way past its prime, IMO. I don't think they're ever gonna be on top.
16) Square-Enix - See what I said for 4
17) SCEA - People still haven't been burnt out on Ratchet, Jak and Sly. They'll need to get more God of War level hits, i.e. original games that do well critically and commercially. Could see things slow down for them as the generational transition occurs and their main developers (Insomniac, etc) come to grips with the PS3.
18) Atlus - They've firmly established a niche. Even though their games don't do rather well, they still keep 'em coming. I never understood why that was, but I'm not complaining (as a fan)

As long as the games keep coming over from Japan they'll do well for themselves. Want to see them have a huge, S-E level hit but I don't think that's happening any time soon.
19) Sega - I *WANT* them to do well after being such a longtime fan, but they continue to make ridiculous business decisions. As retarded as it is, Shadow the Hedgehog should do well, and hopefully PSU lives up to its offline forebearers. Buying up Creative Assembly will certainly help their cause.
20) Activision - Even after all these years, people still haven't been burned out on Tony Hawk. (I thought the series peaked at 3 and rapidly declined since then). When the 3rd Spiderman movie comes out, I'm sure they'll make nice profits on that game. But beyond Tony Hawk and Spiderman, what else do they have? Need more original titles...
21) UbiSoft - Deserves to get hollowed out by EA as they keep on raping POP and won't listen to the fans with a new BG&E.