The cap should have some early winter runs moving in but I am no expert on that system so I am sure others could give you more valuable info than I can.
As for the Seymour there are winter run steelhead in the lower river right now and there are also summer run steelhead over wintering in the upper river. Good access points include Riverside Road and the LSCR's fishermans trail. While there are alot less fish in the Seymour than the fraser valley rivers, there are also alot less guys on the rivers.
For further info on the Seymour I would suggest checking out the following
1) The Seymour Salmonid Societies website (this is a great group that operates the hatchery on the Seymour they are always looking for volunteers, the exciting oportunities they have are second to none in the lower mainland)
2) The GVRD's LSCR website could have some good Seymour river access maps.
3) Stop by Highwater Tackle (around Lonsdale and second) in north van and talk to Dave Steel he is an expert on the North Shore Rivers and the President of the Seymour salmonid Society - he can help you out with seymour river insider info and with info on how to get involved with the society if you are interested.
Good luck and make sure you check the regs for the Seymour if you go it is highly regulated and quite sensitive (there have been changes to the regs this year that are not listed in the print version of the regs that you can only find on the net.)